Unfortunately, this type of response is all too common in real life, and it reflects that one does not have a competitive Pokemon deck. Of course, very few people say this out loud, but they may as well. It is just a fact that most people have difficulty creating a deck which has the qualities necessary to win consistently and at a high level. As a league member and leader, I often see this. Even at tournaments, folks bring decks that are really just fun.
Now, you might ask, "What's wrong with that?" Not a thing... if you never want to compete but only mess around. If you are only in it for fun, you don't have to read any further. But if you are seeking to improve your lot, win more games, and maybe take home a trophy once in a while, take a look at what I have to say.
I have come up with nine (9) elements which constitute a good deck, and I now share this with you. My credentials? I have won a few tournaments and have some glass (trophies) to prove it. I'm not bragging, but only letting you know that I know what I'm talking about. My goal? To help you.
(1) Set-up. What kind of a deck doesn't set up? A slow deck. A losing deck. A frustrating deck. Sound familiar? What can you do about this? You must do two things.
First, make your deck more consistent (see #2 below).
Second, you have to have enough search and draw cards. What are the best choices? In the current (legal) format, you can count on one card: Uxie. Its Poke-Power says it all: "Set Up." Get it, learn it, use it. Two or three per deck. If you can get your hands on Uxie Lv.X, it makes your deck super-consistent, offering by Poke-Power "Trade Off", which is a Pokedex every turn. What else? Poke-Power Pokemon are nice to have, and Claydol was the best (RIP), so you might add a Noctowl or Dodrio line. I am currently testing Dusknoir SF1. You also need Supporters: I recommend 3 Poke Collector in every deck. For SP and SableLock decks, 4 Cyrus' Conspiracy. For Stage 1 and Stage 2 decks, at least 3 Bebe's with a few Poke Communication as well. I recommend at least 2 draw or refresh cards, such as Volkner, Underground Expedition, or Copycat. It's good to have 1 Cynthia's Feelings also. Some people like Poke-Drawer, for its obvious superiority, but the recent spate of anti-Trainer decks (Gengar-Vileplume, Spiritomb starts, and Dialga G) makes that a bit more risky.
You need to test your deck for its set-up capability. How often do you get a "god hand" opening? How often do you have a crisis of search during the game? One of the best decks for set-up is SP, simply because easy searchability and other benefits. Another is SableLock. Stage 2 decks are the hardest to set up, with Lv.X requiring more effort. The easier it is to set up your deck, the faster you will begin to attack/defend and win. Naturally, all good players have good set-up in their decks, so it becomes imperative at that point to find an edge.
(2) Consistency. What kind of deck is not consistent? One which wins here, loses there. One which acts very differently from game to game. Remember, in competition, you're not looking for lots of surprises from your own deck. In fact, the more boring it is, the better you're doing! But I don't mean boring as in "My deck sucks" but "My deck is so consistent that I can play it in my sleep and still win."
When you build a deck, you are conceivably using excellent cards. If that's true, why would you dilute your effectiveness by having two strategies in the same deck? If the strategy is good, the cards which make that strategy good should be maximized. For example, if you play Machamp, you want to have at LEAST a 3-2-3-1 (Basic-Stage 1-Stage 2-Lv.X) line, if not a 4-2-3-1 or 4-3-3-1. Why would you go with 3-2-3-1 instead of 4-3-3-1? Only if 3-2-3-1 was super-consistent, allowing you to add more Set-Up, or special Tech (cards that usually cover a weakness of the main strategy; for Machamp, which is weak to Psychic, Gengar and Nidoqueen have been used as Tech; Machamp also needs its Level.X, so more retrieval is good in this deck; these are Tech).
Not only should you maximize your main line, but also your main Trainer skeleton. For Machamp, you should build with 3 Poke Collector, 3-4 Bebe, 2-3 Poke-Communication, 4 Rare Candy, 2-3 Broken Time Space stadium, 2 Warp Points, 2 Premier Ball, 1 Palmer's, and 2-3 Draw/Refresh cards. You also should include 2-3 Spiritomb, 2-3 Uxie (and Lv.X preferred). For Energy, you need at least 8 Fighting, 2-3 Double Colorless, and 2 Call Energy is not bad either. That is a skeleton, and is consistent. It is also somewhat interchangeable with other Stage 2 decks, as many of the cards will serve the same purpose in, say, Kingdra.
The more you make thin lines (for example, 2-2 Scizor, 1-1 Shaymin, 1-1-1 Bellossom), the more you can expect failure from your deck. However, simply making thick lines won't do it.
(3) Winning Method. A deck needs to be a winner. This depends on many elements, but there is only one simple rule here: the deck must win more often than it loses, and versus very good decks and players. You simply can't walk into a tournament with thick lines and good setup and expect to do better than 50%. Many players have thick lines and good setup. What is your advantage?
Honestly, it doesn't matter why a deck wins as long as it does. If you want to analyze why it wins, that's nice but not necessary. For example, SP wins a LOT because it has many advantages, and even mediocre players can do well with it at tournaments as long as they have a well-built SP deck. SableLock is simple in concept also, but is somewhat more complicated to play, so less players mess with it. Machamp owns SP and Sablelock, but is hard to get just right, so it also isn't common. Gengar also has multiple advantages. Do you see a pattern? It is that some decks just destroy other decks. So, you need to know your metagame (what players in your local area generally play - see below).
Winning is also dependent on your passion for your deck, and (really) its passion for you. Some people love Jumpluff, some hate it. This apples to all decks. Find what you like to play and play it. But... if your deck hates you even if you love it, drop it. You may think Steelix is super, and you may see other players do well with it, but if you're not winning with it, change to something else. For example, I love to play Machamp, and it works for me. One day, I decided to test against SP, thinking nothing of it. I ended up loving SP, and it loves me back, helping me at various tournaments.
(4) Highest Ability. What's the most damage you can do in one turn? Look at Typhlosion, which can do 120 damage for 3 Energy. Or Machamp, which can do 120 for 2 Energy if you roll 4 heads. Luxray Lv.X can do 60 damage for 1 Energy and 1 Energy Gain. Clearly, these are superior attacks. Every situation is different, but in general you want to have Pokemon which have a wicked highest ability. Sableye, for example, can "donk" on Turn 1 - that's a high ability. Pair Sableye with Garchomp C Lv.X, and you have two heavyweights that compliment each other (thus, SableLock). But Sableye has other tricks, such as being able to get a Supporter and play it on Turn 1, the current deckmaster's choice being Cyrus's Initiative, which can decimate the opponent's deck (thus, the lock). Do you doubt me? SableLock won Nationals this year.
Some cards have high ability, but you just can't count on them. Many require coin flips to get the high ability, which is normally not a very consistent thing to count on. Others need their Poke-Powers, which can be shut down in various ways, or on Poke-Bodies, which are in peril by a very popular Dialga G Lv.X currently.
(5) Power Lock. How do you get around it? What if your opponent plays 4 Mesprit LA (Palkia Lock deck)? What about Power Spray? You must consider this if you want to be able to set up, be consistent, and have your highest ability available.
Since Power Spray is more common, you only need to be concerned about an early string of them. Get past that, and you might win handily.. maybe. If you have a Stage 2, or even a Stage 1 deck, Spiritomb AR is your boy. It helps you set up with Darkness Grace, and disallows Power Spray from play due to its Poke-Body. Of course, it stops you from playing Trainers also, but that's the trade. Gengar SF with Spiritomb is a good and deadly combination.
(6) Body Lock. As already mentioned, Dialga G Lv.X cancels Poke-Bodies which are not SP. It's common, but not overbearing.. yet. Just remember that you take a chance every time you rely heavily upon Poke-Bodies.
(7) Low Energy to High Damage Ratio. Why didn't I just say this already? Basically, because most people know this is good, whereas they don't know as much about other elements I have discussed.
Machamp. Kingdra. Jumpluff. Gengar. These all use 1 Energy and offer a high ability for it. That's why they are called "top-tier" decks. Nevertheless, they have suffered by the rotation of Roseanne's Research, which was the one Supporter that made such decks super-playable. Without Roseanne's, it is difficult for many decks to get that Energy necessary. SP and SableLock, on the other hand, have Cyrus's Conspiracy, and so have a great advantage in the current format. Scizor Prime can sort of count of Skarmory for Energy attachment, and Steelix can kinda count on itself, but these are not the best substitutes for consistent and simple search-attach options.
On the other hand, given Kingdra or Feraligatr, Kingdra is superior even with Feraligatr's Poke-Power. In the first place, Power Spray. In the second place, you need Energy in hand. In the third place, Spray Splash. In the fourth place, retreat cost. So, you see, there is Energy cost and there is Energy cost.
(8) Comeback. Look, the truth is that no matter how well you play you will eventually come to a time when you are behind on prizes. Do you fold? For some decks, that is the only option. High-Energy decks are likely not going to come back against Low-Energy decks which have a substantial lead. Yes, it is mostly about Energy. Face it: 1-Energy can be achieved quickly, and repeatedly; multiple-Energy cannot.. at least, not consistently.
Now, if it's a battle between low-Energy decks, how can you come back? This is where Tech comes in. Perhaps you have a secret weapon to counter your opponent's main attacker, and quickly. For example, SP is behind in prizes against Machamp. It looks hopeless, but wait... Double Colorless Energy on Uxie X, Lucario GL in play, drop the Crobat, and take the Machamp. Opponent tries to use Uxie, but SP drops the Power Spray - denied! With no setup, Machamp passes, and SP then is able to set up a Garchomp C Lv.X for another prize. Do this, gain the edge, and climb back to even, before you pull out the victory! Yeah! Nothing better in any game or sport than the big comeback. Your deck should have this capability.
(9) Matchups. This is the metagame. Who plays what, where, and why? Let's look at the current spectrum, and do matchups against LuxChomp (SP).
Jumpluff: A powerful card. Without Claydol and Roseanne, it has real trouble vs. SP.
Machamp: SP can look forward to a hard time, unless SP sets up faster, or Machamp stalls.
DialgaChomp: Fairly even, but DialgaChomp players are getting feisty.
Gengar/Vileplume: If SP can't play trainers, it loses. This can go either way based on speed.
Gyarados: Generally a win for SP, Luxray GL doing the main work.
Donphan: On paper, Donphan wins easily. In practice, Donphan isn't that great.
Charizard: For the most part, easy.
This matchup list is only a sample, and very oversimplifed. Decks change with each new set release, so the matchups change also. Furthermore, it depends on Tech, your opponent's skill, and LUCK!
Well, kids, that's it. If you follow these general rules, think about what you're building, and stay focused, you will do very well.