1. C&C Tiberian Dawn
2. Starcraft
3. Ultima Online
4. Everquest 1
5. Renegade
I almost put counter strike instead of renegade, but I think in the long run renegade ended up being more enjoyable. I am a bit reluctant to pick the newer games like C&C3 etc, simply because they have not had to endure the "test of time". Games today are built to sell and replace, they are not designed to last a long time.