It is Fable 2 .In the start I was reluctant to buy it even because I do not like such type of games (RPGs).But After playing it,I was addicted to it.Its too many gameplay elements made me interested more and more every time I play.It scored many awards in my "Book Of Games".

Runner Up is Grand theft Auto 4.Niko Bellic, My favourite hero of 2008.It was versatile game.And It scored more awards than Fable 2 but for the first time I had to entitle the GOTY to the one who scored second.I did that because, for me Fable 2 was Revolution.A new game, a new experience that I never had before.A totally different and remarkable game for me.So

REVOLUTION OF 2008 is FABLE 2

Runner Up : Grand Theft Auto 4

Other honourable mentions :
Gears of war 2, Call of duty 5, Left 4 Dead,Euro 2008