I really like my original fantasy worlds. I cannot even begin to describe how I feel about in-depth worldbuilding and getting to explore that. But I also really prefer linear RPs with defined goals and unavoidable character interaction, preferably something involving them working together to overcome something else.
The number of RPs that tick all those boxes is unsuprisingly limited, especially given the current trend of sandbox RPs and such, inspired I assume by the current trend of sandbox in video games (which I also tend to end up not enjoying as much). But honestly, I've RPed in and enjoyed a really wide variety of genres and such, since anything with an interesting premise will draw my attention. Although, back in the day, I had a weakness for the then-common "your character is one of the chosen ones and has powers/legendaries/whatever and needs to save the world!" type of RP. It's such a cheesy and cliche kinda RP, and yet I always had so much fun. xP
But aside from all that, I prefer RPs where my character is forced to confront and react to situations and people outside of my control rather than have to work in stories or events or npcs myself. That's honestly when I have the most fun RPing. ^^