I can’t honestly think of any mainstream media I’ve seen that has RPGs in it at all. I guess that means nothing has been particularly memorable. Actually, now that I think of it, Knights of Badassdom was mildly amusing and based around LARPs, but it wouldn’t really qualify as anything I’d call my favourite.
Actually, come to think of it, I remember fondly when I was reading the Dresden Files series of novels and roleplaying was brought up in those and the characters in the book actually played a game. It was one of the first genuine, non-snarky inclusion of roleplaying in I’d seen in anything, and it was a just a nice moment among friends that demonstrated roleplaying games as something that brings people together to have some fun.
Outside of more mainstream media, I guess my favourite instance of RPGs would be watching Dread played on Tabletop. Wil did a fantastic job of building the tension and story in tandem and it was by far one of my most enjoyable Tabletop episodes. I’d say I actually enjoyed it more than the Titans Grave RPG show that’s ongoing, or the Dragon Age one. Not to say those ones are bad, but something about the delivery and simplicity of Dread makes it really stands out for me.