I don't really have a favourite. RPGs are fantastic provided there's genuine roleplay, levelling up, great quest rewards and ways of changing the world based on your actions. Those kinds of things make me feel as though I'm actually achieving something in the game and not only is it sentimental, I can see the results for myself.
Strategy games are also good, but what I like now is to melt my brain with mindless shooters. Some games like Rainbow Six where basic brain function is required I like, but other times I like 'duck 'n' pop' gameplay to sate my laziness.
But my heart lies in platform gaming. The genre was dominant years ago and went into a slow and painful decline. It had such great titles which even now I play on a regular basis and not for rewards and entitlement but simple fun. Today it's proving popular by advancements in the Super Mario franchises, Ubisoft's reworking of the Rayman series and new games are coming to the block with confidence, especially now that Indie gaming has developed so much in short time.