I think any RP has the potential to be popular if you think up a good plot.
But I voted chicken: I don't RP much anymore, but I used to have fun doing the chicken ones.
You should really start a RP that interests you. If your passionate about your RP it shows vs some role plays that people opened because other people liked the subject matter. As long as you chose one you like and have a well thought out plot I'm sure you'll get people to join you.