FPS - Counter Strike. Singleplayer would be STALKER. Played for a few minutes. Was absolutly brilliant. CS rules though!
Space - Havnt really played any. X2 was sooooooooo boring
RTS - Played C & C red alert for around 5 mins. Hard to get in to
Adventure - Mafia (still playing) Brilliantly cinematic.
Action - GTA Vice city. (SA sucked, to much attitude). Pure fun

Online - Counter Strike Source. How could it not be. Only one other person thought so. It must be dying out

that would be the end of an era.
RPG - Morrowind all the way. Oblivion was such a let down. Man I loved stealing a house and collecting stuff.

Many a thousand hour I wasted collecting pots and stuff worth 1gp
GodGame - me playing with ants?

Dont really play any.
Car - Probably NFS-Most wanted. Kept me entertained for ages. I remember a previous nfs. I think it was hot pursuit 2. Played years ago on demo and wanted to buy it.

never could find it.