Best pc-game i've played is by far World of Warcraft (Vanilla NOT TBC/WotLK etc.). When it was new and fresh, the experience is unforgettable. Before anyone was 60, before epic gear was viable for everyone, WoW had everything. Great score, superb gameplay, beautiful scenary - a feeling ill never forget and the only game that, in my humble opinion, is on par with - yes - The Legend of Zelda: Ocarina of Time (n1 game ever - if you havent played it you can NOT call yourself an ultimate gamer). The reason it was double epic was that , ,though a newb, i got in the n1 guild of the server and we had the first server kill of the boss ala bosses of Vanilla WoW (Ragnaros - Taste his flames :)!!!). Back then, that was a huge accomplishment for me :P

Besides WoW, personally Counter-Strike as the omega plus first-Personshooter game till CoD/Battlefield 2 came out. CS 1.5 was the most fun time i had with a multiplayer FPS (being 14 years at the time). Besides CS, Unreal Tournament with my nephews was also unforgettable and UT>Quake 3 all day!.

The game with the most intense story-telling (though not original made for the pc) for me is The Chronicle of Riddick: Escape from Butcher Bay. Im a sucker for a good plot and sick atmosphere in a game and Riddick scored 10 on both levels.

As for RTS its a war between Red Alert 2 en Warcraft 3 where Warcraft 3 wins in singleplayer/storytell (very Epic) and Red Alert 2 wins @ Skirmish and LAN fights.

I never played Civ, The Total games or Deus Ex, but i do think the latter deserve to be in the list too.

All in all the best for now is WoW Vanilla, yet if you hadnt played it from the start you won't know the feeling of it!