I love Star Trek, but I think the Federation would soooooo boring - unless you could hang out with space hippies.

Star Wars might be fun in the places not touched by the Empire, but you could easily get killed.

I think the most fun would be either Doctor Who or the Hitch-Hiker's Guide, which I suspect are actually the same universe.

As for fantasy, I was going to say "anything other than GoT," but Mighty Boosh counts as fantasy, doesn't it?