I play almost everything cross-platform on a gaming PC, so "on PC = not console X exclusive" really is the way I think.
To me, Mass Effect 1,2, Dragon Age, Oblivion, Fallout 3 & New Vegas are all PC games that also happen to be available on one or more of the consoles I own.
To me, Crackdown 1,2 and Valkyria Chronicles are the "real" console exclusives since I have to fire up my 360 or PS3 to play them.
But I do understand for those without a gaming PC that Mass Effect 1 really is a 360 exclusive and DC Online really is a PS3 exclusive. Of course if you own both consoles that doesn't matter either 🙂