Ah, now you made me look at my terribly long list of all the games I ever played (and remembered)... It does indeed require some very tough decisions, but here's my attempt:
1.
Heroes of Might and Magic (3, then 2, then the rest). Awesome game - played it and all the expansions again and again for years, both campaigns, one-off maps and multiplayer.
2.
Civilization 2/3/4 - being close to god just rocks!
3. Guess I have to say the
Command & Conquer genre - all the way from Dune 2, through the first C&C, Red Alert to Generals Zero Hour. Along with the warcraft series, this series the bar I reckon. Played them all.
4.
Little Big Adventure 2 (1 was save game bugged). Fun, compelling, cute and imaginative - great action/adventure game.
5.
North & South - many fond memories of childhood multiplayer games in this one
- excellent replayability vs. humans.
Runners-up...
6.
Ecstatica 1/2- unique and
very atmospheric/eerie.
7.
World of Warcraft - it did steal roughly 2400 hours of my time...
8.
Max Payne 1/2 - with it's original slow-mo bullet time action and nice film noir setting, I'd have to say it's been the most interesting Shoot-em up I can recall.
9.
Warhammer - Dark Omen. Perhaps not the greatest game, but as a warhammer player it provided me with the opportunity to see my miniature toy soldiers come to life
10.
Far Cry - I personally loved the beautiful graphics and nonlinear 'walkthrough'.
11.
Star Wars Pod Racer - Awesome speed!! (with the best racers in late game) - nice graphics and atmosphere too.
... + praise to those forgotten here! (Only naming 5 is clearly not possible
)