I got a 50" LCD tv on my living room, and games never seem to look right, i already used the THX Optimizer that came in a star wars movie i got, and no change, movies look perfect, same as tv shows and that kind of stuff. The main problem is that games look too dark (Demon Souls is impossible to play on this tv), i already tried turning the brightness and contrast all the way up and still does not looks right. The PS3 menu before getting into a game looks right, so that made me believe i have to change settings in the ps3 display settings.
Does your tv have different modes like theatre, gaming, custom, and such. If so, try changing it to gaming mode.
it has vivid, standard and movie, vivid is brighter but games still look too dark, i believe it has to do with the ps3 settings because the menu before you get into a game looks right, its with the games, movies look fine too