My picks from the last two years or so:
Rise of Legends
Company of Heroes + expansion
Command and Conquer 3
World In Conflict
Myth 1 and 2 from pre-MS Bungie had great single player games.
I always thought it was interesting that the stories/presentation in the Myth games seemed more compelling than the books most of the lore was riffed from (Glen Cook's Black Company series). The stories in both games are very, very well presented-Halo's a big step down in presentation in comparison.