I love the AI War soundtrack. Most soundtracks for space strategy games you hear are mostly along the lines of epic symphonic pieces, but AI War's is mostly subdued and melancholy. This is really fitting, because AI War is pretty melancholy game when you get down to it. The huge battle that warranted epic symphonies already happened, and you lost it. Badly. Most of the human race is dead, and the thousands of ships lost during the game just stretches it thinner and thinner. The game has a very tired, regretful, but ultimately still hopeful feeling about it. It's one of the things that really makes the game stand out to me, and I feel that your music captures that feeling very well.
Also, I haven't seen it given much love in this thread, but one of my favorites is Birth of the Golems. The second half never fails to get my foot tapping, though I thought it was one of the few that didn't really benefit from the remaster. I liked the pseudo-electric guitar melody near the end, and the switch to the organ, while not bad, doesn't really seem to fit as well with the rest of the song in my opinion. The remaster did wonders for the others, though. Marisa didn't really stand out to me before, but now it's up there with Midnight.
The only song I dislike is Neinzul's Title Theme. The trumpet part is grating, and the rest of it is pretty forgettable. It had a hard act to follow after Zenith's Title Theme, but even so, it's pretty below the bar set by the rest of your music. Still, only one or two bad songs out of 28 is great. Whenever Chris announces a new expansion, one of my first thoughts is always "Awesome! More music!"
Finally, this may be a long shot, but piano has always been my favorite instrument, and the piano tracks you write are brilliant. Do you happen to have sheet music for your songs? I would love to be able to play your stuff, especially Midnight, Marisa, or the Zenith Title Theme.