There's plenty of winning decks:
Luxchomp
Vilegar
LostVileGar
LostGar
Dialgachomp
Sablock
Chenlock
Gyarados
Machamp
IDK how this is stale really...
I'd say the format is diverse-ish.
Now let's take those decks and separate them out according to their strategy:
Speed: Luxchomp, Dialgachomp, Gyarados, Machamp
Trainer Lock: Vilegar, LostVileGar, Dialgachomp
Other Lock: Sablelock
I don't really consider LostGar without Vileplume as a "winning deck." Aaron Curry's the only guy who did anything with it. And I lumped Chenlock into Sablelock since it's basically the same strategy anyway. It's hard to argue for Steelix and Magnezone since, from a State-winning perspective, they did as good as Arceus did.
Porii, I have a feeling you're going to disagree with me no matter what I say, so I'm really posting this more for other people than you. But I do hope you truly consider what I'm saying, since it bears a great deal of weight on our current format...
When I first got into this game, there were tons of strategies that people could use to win tournaments. I just talked about this on another thread where I listed a number of decks that, within a two-year period, could win tournaments. Here are those decks: MetaNite, Flariados, Dragtrode, Ludicargo, ZRE, LBS, PowCham, Metro, LunaRock, Destiny, Mynx, Raieggs, Flygon d, Rock Lock, Spin Tail T-Tar decks, ZapTurnDos, Dark Slowking, Machamp/Pidgeot, Queendom, Speed Banette (or BanDoom), MewTric, Eeveelutions/Pidgeot, Jynx swarm, Speedrill, Salamence d, Polistall, Shedstall, Mercury, Scythe, Speed Scizor, Absolution, FlyCatty, Speed Arcanine, BanCham, Scrambled Eggs, Muk Lock, Huntail/Gorebyss, etc.
Here are the other post I made concerning these decks:
here. Also, I forgot some other decks like Dark Steelix, Dark Slowking, and Jumpluff, among other rogue-ish type decks.
The thing about those decks is the variety they provided to the game, strategically speaking. MetaNite had variable damage and used two Stage 2's, Flariados was all about special conditions, Dragtrode manipulated energy and could hit hard or play defensively, Ludicargo ran every tech imaginable, ZRE was disruptive and fast and just insane, LBS was a powerhouse of a deck, Powcham locked Poke-Powers and spread damage, Metro was the Metanite across the pond, Lunarock was an all basic speed deck, Destiny was a counter, Mynx was a mind-blowing lock deck, Raieggs was a spread, etc. etc. etc. Almost every deck had its own viable strategy.
Today I see everything setting up by turn 1 or turn 2 unless someone's playing a trainer lock deck. That's about the entirety of the format: speed and trainer lock. Even trainer lock has to be speedy, since a single turn of letting a Gyarados player use trainers can mean a game loss in the end.
I'd like to write out some lengthy answer to the original post, but I don't really have the time (have to go volunteer). In any case, many people have hit some good points. SP is overpowered with its own exclusive trainer/supporter engine, it's been around for far too long, and it kills the potential strategies that this game could see. Also, if SP weren't around, I'm sure you would have people hating on Gyarados for the same thing (even though I played Gyarados at both States, I still can't stand the deck). So it's not just an SP thing, it's the overarching polarity the format has right now in terms of strategy. You either play a blindingly fast game or you
hope to play a menacingly slow game... either way, it's boring to me.