Might not be the most simple game, but Final Fantasy 7 for the PC just got an update to make it compatible with newer OS versions. While I personally think the game is a bit overrated -- it's a good game to be sure, I just don't think it's worth the level of veneration some people give it -- it's still a solid RPG.
The original Dawn of War series was actually pretty good. The first game had a pretty good story on the whole, the Winter Assault expansion you'd be better off just skipping IMO, but Dark Crusade and Soulstorm are both pretty good despite having only a paper thin plot. You may even end up like me, and get hooked on the various book series' set in the same universe.
If you play Borderlands, be prepared for one of the single most anti-climatic endings of any game ever. Rest of the game isn't too bad through.
And you also can't leave out StarCraft, either the original or StarCraft 2. WarCraft 3 wasn't bad either, and Blizzard is usually pretty good about updating even its old games.