It changes with time, but here are some :

1. The Sims 1 & 2 + All Expansion Packs
2. GTA III, Vice City & SanAndreas
3. Prince Of Persia (Its not sands of times, warrior within or The Two Thrones, its one that was released in 1991 and its the first ever game i played on PC when i was some 5-6 yrs old :D)
4. Price Of Persia The Shadow & The Flame (Second Part OF The Above One, its damn difficult, never ended it but made upto the last level)
5. Age Of Empires III
6. Midtown Madness 1 & 2
7. MOHAAA
8. Call Of Duty II
9. Max Payne
10. Dark Reign 2
11. Need For Speed Most Wanted Black Edition
12. EA Sports Fifa 2000, 2001, 2002, World Cup, 2003, 2004, 2005 & 2006
13. EA Sports Cricket 2005
14. Battlefield 2 Special Forces
15. Pacman (Can't forget this classic game)
.................................................. .................................................. .................................................. ............................................... and the list goes on :D :D :D :D :D