Media Molecule, That Game Company and Quantic Dream for me. Potentially Naughty Dog and Obsidian, depending how their next games turn out. Bioware and Maxis get a zombie vote. Double Fine, Bizzard, Valve, Kojima Productions and Square Enix get runner up awards, reasons below
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The thing about Valve, is they literally couldn't do what they do without Steam. The reason their games are so polished, is they don't actually have to make money on them. Look at Half Life 2, that game probably didn't even start to make real capital for them until 4 years after it was released. But it didn't matter because they had another source of income suddenly coming in and they could still employ their people whilst they waited for the sales to build up. Valve without Steam would be like Obsidian, having to scrape around with publishers making games they don't want and being forced to release games early.
I mean the fact they can just not release a game for 5 years because they aren't done is incredible, no other studio could tie up so many millions and millions without a return in sight without going bankrupt.
... but on the other hand, having Steam Valve have used it more responsibly than almost any other publisher apart from the GoG guys would and having Steam they pay their games much more attention than even maybe Blizzard and they're willing to try out new cool things with Team Fortress. So I'll give them a 3/4 vote.
Then... probably Obsidian. KotoR 2 is a freakin' amazing game and so is Planescape. The test will be Project Eternity, if they can actually deliver and without publisher interference their problems go away they'll forever win and get my vote. But if Eternity is buggy even though they're the ones doing QA, then they can't quite be my favourite developer.
I like Double Fine, even if I'm not particularly blown over by their games, they have a strong identity and do things in a good way.
Bioware have been a bastion of RPGs, but Bioware has gone the way of Maxis. It technically exists but it's hard to place exactly what is Bioware and whats a label. So Bioware and Maxis are my walking dead choices.
...as much as I love Metal Gear Solid I don't think I can give a best developer label to someone for one games series. Equally, I love Final Fantasies and I love that they innovate and change so much from game to game, but all the sequels for XIII make me think they're a bit money grabbing sometimes.
the issue is they are a publisher now, which is not a developer, if the question was favorite game related company, by all means answer EA, everyone has different tastes, but it seems to me like you are the one that can't deal with the idea that no one is actually attacking them, they are just pointing out that you are giving the answer of mandarin orange to the question of what is your favorite type of apple.
