In no particular order (other than VC:MP being #1 obviously)
1) VC:MP
2) Rise of Nations
3) AoM
4) Unreal Tournament (original and 2004)
5) Transport Tycoon Deluxe
6) Theme Hospital
7) Dungeon Keeper
S.T.A.L.K.E.R Shadow of Chernobyl
9) Call of Duty United Offensive
10) San Andreas