My list:
1. X-Com UFO: Enemy Unkown:
Played it, loved it.
2.Silent Storm:
UFO Enemy unkown+World War 2=Silent storm.
3.Legend of Zelda: Ocarina of Time:
*sniff* Very fine, my second favorite game ever, very memorable.
4.Legend of Zelda: Majora's Mask:
No matter what people say about this it's still one of my favorites. I just loved playing with the masks and finding them.
5. Jedi Knight: Dark Forces 2 and Mysteries of the Sith expansion:
I haven't got Dark Forces, but if it's better than this I'll cry.
6.Indiana Jones and the Infernal Machine:
A 3D action adventure. It was fun. And the bazooka with monkey island cheat. :P
7.Warcraft 3+Expansion:
197 hours of gameplay should be enough. Very fun online.
8.Hercules the action game:
Best.. Licence game.. Ever.. It's fun, features reasonable graphics to todays standards and never gets boring.. Classic.
9.Neverwinter Nights+Expansions:
D&D on PC with great graphics and easily expandable, veeery fun.
10. Guild Wars:
Very nice MMO with no monthly fees. Very fun.
Honorable mentions:
Battle for middle earth 1 & 2.
Medal of Honor: Allied Assault
Elder scrolls Arena
Shadow Grounds