Well, I'm pretty sure I've listed them before, but it is worth repeating:
Dungeon Siege 1 (I know this belongs to Square, but still.)
Age of Empires series
Age of Mythology (The real one not the remake, they seem to have changed the art style.)
Hey, why not dream, let's have Halo 1&2 on here, not that they were wonderful games or anything. (Actually, I paid a lot of money for Halo, I'd probably not buy it on here.)
Mech Warrior/Commander series (Unless it changed hands again, which it probably has.)
Gears of War
Crimson Skies
Close Combat series (I think Microsoft had something to do with that.)
Flight Simulator
Combat Flight Simulator
Rise of Nations series
I guess their attempt at ruining Shadowrun for completion's sake.
Maybe PC ports of classic Rare games like Conker's and Banjo.
Microsoft used to be so big in the PC games industry, then they seemingly just decided to quit (after unsuccessfully trying to force Windows Vista on everyone). So sad.