This question is evil. One does not simply have a 'favourite game'. If i'm looking for some quick fix/satisfaction I'd say Osu is my favourite, In terms of best gameplay and overall most fun i've had on a game (not to mention 3000 hours gametime clocked) I would say Final Fantasy 12 for it's sheer size and complexity, you could play it for years and find new things about the game with each play. However if i want a game to truly test my reflexes and technical skill, Osu, Guitar hero and games of that nature would be my favourite.
Seriously i'm just scraping the surface of what i want to say here, this question has destroyed me.
Seriously i'm just scraping the surface of what i want to say here, this question has destroyed me.