18th) Favorite SF RPG
Serenity RPG. Despite being a huge fan of SF fiction and film, I've played and run very few SF games. But the most fun I've had in this genre was in my friend Mike's Serenity game, playing my daredevil pilot Zefira.
19th) Favorite Supers RPG
I play even less supers than I do SF, so I don't really have any favorites here (for campaign or system).
20th) Favorite Horror RPG
Buffy the Vampire Slayer. I mentioned a few days ago that one of the longest campaigns I've played in used this system and setting. Also, the rulebooks are entertaining to read--which is a challenge when writing RPG rules. The Cinematic Unisystem rules this game is built upon was also used for Angel, Ghosts of Albion, and Army of Darkness, and my group stole shamelessly from all three for our "Grey Angels" game.