Just as an FYI for anyone having trouble starting Supreme Commander 2, I recently just figured what was causing me being unable to start the game.
Apparently the programmers didn't account for the possibility of the user changing monitors, because I went from a 1920x1200 (the game always worked fine then) to a 1920x1080, and then the game would never successfully start (it would kinda flicker in an attempt to change resolutions, then simply return to desktop without displaying ANY error message - quite frustrating).
To fix it, one can create (or simply log in) as a different user in windows, then start the game as it will begin in the default 800x600 or so resolution, which virtually every monitor will allow. Hope this helps someone, as it was really bothering me.
I had this issue as well thanks for the post, pointed me in the right direction, but instead of creating another user account just go and delete the game.prefs in appdata/local/gaspoweredgames and then it worked like a treat for me.