Heh, between all the NES, SNES, N64, GCN, GB, GBC, GBA, PSP, PS, PS2, X-box, and PC games I've played it's hard to even do a list of thirty.
But, here's my best shot.....
30. Advance Wars (GBA)
29. ActRaiser (SNES)
28. Star Craft (PC)
27. Call of Duty (PC)
26. Splinter Cell (X-box, entire series)
25. Fire Emblem (GBA)
24. Mega Man X (SNES, X, XII, XIII)
23. Halo (PC)
22. Total Annihilation (PC)
21. Star Wars X-wing Alliance (PC)
20. Star Wars Rogue Squadron II (GCN)
19. Command and Conquer (PC, entire series)
18. Tetris (Gameboy)
17. Earth Bound (SNES)
16. Castlevania (ones the Playstation, GBA, and SNES)
15. Lumines (PSP)
14. Final Fantasy X (PS2)
13. Final Fantasy VI (SNES)
12. Metroid Prime (GC)
11. Final Fantasy Tactics (PS)
10. Chrono Trigger (SNES)
9. Final Fantasy IX (PS)
8. Super Metroid (SNES)
7. Super Mario RPG (SNES)
6. Metal Gear Solid: The Twin Snakes (GC)
5. Super Mario World (SNES)
4. Metal Gear Solid 3: Snake Eater (PS2)
3. Knights of the Old Republic (PC)
2. Super Mario Bros (NES)
1. Ocarina of Time (N64)