Hmm it could be the fault of so many large images. My Animations folder in Windows Explorer says I have 5,000 files (and C2 tells me I have 4,000 events). My project is an RPG, so some of that is understandable, but I also generally have smaller objects than you might in a fighting game.
On preview with chrome closed:
9 seconds on "Starting Preview" in C2
29 seconds on the loading bar in Chrome.
So it takes me 38 seconds to run a preview, but for the size of my game, that seems pretty understandable. I never get a red bar, though.