I find RPs quite fun sometimes, mainly serious ones on IRC. An outright insane 'RP' tend to be funny at times, but overall serious ones are more fun. It was a while ago since my last, though. When it comes to serious, though, it starts to become a problem (For me, for some reason) when vore is involved.
A nice vocabulary and large imagination is what's needed for a decent RP.
This is only IRC, however. RPing anywhere else... I find rather stupid, unless it's an actual game made for roleplaying.
Heck, role playing doesn't neccessarily have to be a "i'm this, you're that. I do this, you do that." sort of thing; Halo 2, for example. Me and my friend take roles for it, he's a sniper and gunner in warthogs, while I'm a driver and fighter. Go battle rifle. Apart from that, it's just a normal Halo 2 game, as we always use the private chat function in Live or Windows Live Messenger. (On a side note, we're virtually unstoppable in a Gauss Warthog.)
If there's a game like WoW (Neither of us play that, I'm not too fond of the pay-to-play), then I could see us really getting into character. Well, me, at least. i'm that kind of person.