.. this is a very wide market, so there is no company best, but The makers of Angry Birds, are doing a real good job, not just creating the game (i don't like it at all), but it's the marketing around, specially on mobile devices, which is most important ^_-
I mean, ubisoft etc, can make it too, will cost u a ton more, but, it's just an example.
One of number 1 sold games called doodle jump, was made by 1 person from hobby afaik, so u know.. Can be anything