Fantasy or Modern-Super Hero like stories, I suppose. They both offer a lot of freedom, both in world and character design. A lot can be made out of 'nothing' to really create a story and setting unique to me and whomever I'm RPing with.
Likewise some 'slice of life' stories are a lot of fun as well. I like character building. So having a story that doesn't revolve around not being killed by monsters or villains, just living a life and meeting the love of their life (or just flings) and the like...living a life that is more eventful than my own, is a nice change of pace.
If we go 'kink' wise, I am scum and enjoy incest plots a lot due to the uncouth nature of it. How the characters react to the deed before, during and after. The compulsion to keep it secret. Deciding to keep it going or end it after that one time. The psychological side is fun for me, I suppose. Not just the smutty fun doing the scenes themselves.