My top 5, not in order, would be:
- Call of Duty 4. It wasn't revolutionary in any way, but was certainly evolutionary. Notice how since CoD4 most shooters have tried to be like Call of Duty?
- The Sims. I think this game was 2000's right? Or was it late 90's? I dunno either way this is one of the best PC games ever.
- Gran Turismo 3. Probably the best game in the GT series, which happens to be the best driving simulator franchise ever.
- Halo CE. This game proved console FPS games can work and started the awesome control scheme that has been used ever since. Has massively better controls than Goldeneye on the N64.
- Fallout 3. Probably the best RPG I've ever played and the most fun. I'd play this over Final Fantasy any day.