Favorite roleplays....hmmm....where to start
First of all, from my experiences, the favorite ones are where both players with roles actually enjoy their roles. I have no doubt that many approach you with a self centered fantasy which they have evolved for many years, and try, probably incoherently to spit out in a few short sentences or paragraphs. And I have experienced many Dommes who assume that they can control the play without regard for the fetish interests of the sub. One can only have dominion over pleasures, meaning that a subby into domestic discipline will most likely not enjoy heavy latex and bondage roleplay, and likewise, a Domme not into some things will not enjoy creating a play that become just work.
Now that said, I am most enticed by traditiional domestic discipline, with Dommy Femdoms, which starts with confession, then subby being ordered to strip naked, scolding, humiliation (which requires understanding of parameters), having Dommy's friends witness, belt spanking after corner time. Now, if face slaps or spits are infused, or foot (or other areas) worship , and sissy dressing and peg activities are included, then those would not be bad.
Having worked for clients in Bangkok for a few years, I have learned that anyone who says they like everything is either naive, lying, or a psychopath When you leave a place like that, you have no fantasies in the sense there are things you have fantasized about, but have not done, because in a place where you can literally do anything (and trust me most people don't understand what "anything" literally means), you leaving knowing exactly what you will or will not do. But if you engage in a transactional association, then both roles have to understand why both players choose to engage. A Five Star steak house and Golden Corral both offer steaks. In role play, both have to understand that one is a bargain at any price, because of the service and attention to detail and the artistry provided, and the other has to understand, that you get what you pay for.
Okay, that was long, but You asked a very real question, so I gave an answer that I think tried to show it deserved more than a cursory reply.
What might YOUR fav roleplay be if I may ask?