Unlike the "writer" thread, this is not about anything specifically art music or writing, so I'm moving it to the Tavern.
Also I would advise the OP that making many variations of the same kind of thread eventually starts to look like a play for points, unless there's a real plan for all of it.
ConArtists is my favorite. But to be honest, anyone who can make an awesome zombie game is up there pretty easily. Outside of AG I really like Capcom before their writing got silly. Pandemic is a favorite too.
It's arguable that Conartists or John are the best. Conartists has awesome games like Warfare and the Last Stand, and John has great games like Hedgehog Launch