I've played just about everything under the sun, but I think my favorite system will have to Hero System. My biggest pet peeve as a super heroic gamer is people wanting to play as the well-known characters of their favorite comics/movies. I find it to go against the spirit of role-playing. Once you sit down to play the Marvel or DC games, everyone just fights over who gets to be Superman or Captain America. Hero system puts such a high cost on cool powers that you can't play like that and are forced really to use your imagination , which I feel is the spirit of role-playing.