No one hit wonders. Said game studio needs to have released at least 3 quality games and they would be judged as a whole. So no "Released one excellent game and two dogwater games". CD Projekt Red fails to make the list because as far as I am concerned they've only made one, arguably two, quality games.
IP diversity is encouraged. It is not an automatic disqualify them but it does weigh against them if their entire thing is just making one series of games. Perfect example is Team Aces who only makes Ace Combat and nothing else.
No generic in house devs for major publishers. So no Nintendo, Sony, Microsoft, EA, Activision, Ubisoft, Square-Enix, Capcom, Konami, Bandai-namco, etc. The reason why is because they tend to shuffle staff and dev structure so often that they can't really be judged as a whole.
But second party studios of major publishers are allowed. Intelligent systems, Sucker Punch, Rare, Obsidian are all eligible.
With that in mind here's what I have so far:
From Software Treasure Sucker Punch Insomniac Naughty Dog Level-5 Monolith (both of them) Bungie Genki Clover Studios Platinum Games Rare Obsidian