What’s The Culture? My answer is the Star Trek universe. 95% of people in that universe never have to even think about the Borg or the Jem’Hadar or even combat of any kind.
Middle Earth, definately. So I can get Elfed.
Any universe where I can get cool powers would rock.
A D&D universe (I am most familiar with the Realms, so probably that) would be nice, but gosh darn it, I like technology.
The Marvel universe is pretty sweet. I could hope to be a mutant, or failing that, just go one of any number of super scientists and have them pump me up. But humanity gets threatened an awful lot over there. Lots of worldwide destruction.
I think in the end, the Buffyverse is my pick. I can learn magic, or become a vampire and win back my soul. Of course, the hard part is after becoming a vampire, actually wanting to get my soul back. But hey, I think being a vampire, even an evil one, would be cool. I’d also be one of the smart oens and stay at least 1000 miles away from the slayer at all times.
Of course, I could also just go to the Trek universe and live almost my entire life in a holodeck that is just like the Buffyverse, and then I could even play around and decide whether I prefer having magic powers, being an ensouled vamp,. or some kind of demon. And hey, no fear of death (as long as the safety protocols don’t go offlin e. But that never happens.)
I’d like to live in Bedford Falls and commute to Central City.
Trek of course
Middle Earth would be great but I would miss the Tech, but I love to have visits.
The multi-verse of Lazurus Long whould be great, I would choose one of the High-Tech golden ages.
Jim
I’ll just second The Culture.
I’d like to live in the universe that’s portrayed in every porn film that I’ve ever watched. 
I’d go for the Hyperion universe…I persoanlly would have no objections to have the rooms of my house spread out over a multitude of planets
Futurama! There are limitless entertainment options, like riding a T-Rex or going to the end of the universe to see your cowboy self, and you can actually go inside the internet. Plus there’s all the baconated grapefruit and molton boron you can eat. Ok, occassionally your whole planet might get challenged to a game of basketball (loser is a jive sucker) or have your nose (or worse) harvested as human horn, but that is what makes life exciting.
Fine, so this whole post was an excuse to mention some of my favorite Futurama references. It would still be a really cool place to live.
Take a walk and wind up in a different universe.
Yeah, until the Hyperion novels actually happen and you get cut in half walking to the bathroom though.
If you’re thinking of what I think you’re thinking of…the one which Batou accidentally got some feedback from–
[my head asplode]
As for me…hmm. Maybe the world of Howl’s Moving Castle, either the book or the movie. Each has its appealing elements…
Middle Earth. Until I needed modern amenities. Then I’d go to Cicely, Alaska (of the “Northern Exposure” TV series).
Narnia, in the golden age of the four kings and queens. But the revival under Caspian would be bad either.
That’s *wouldn’t * be bad either!
I’d like to live on the Isle of Riva under King Belgarion. Or, failing that, Deep Space Nine.
Well the OP states universe not the actual novel. I doubt all the ones posting Middle-Earth would necessarily live there during the events of LotR.
Andre Norton’s Free Trader society seems fun.
As does the out-system life in Robert Heinlein’s juvenile novels.
Zenna Henderson wrote about telepathic aliens marooned on Earth. I’d really like to be one of the People.
And finally, the Wold Newton Universe sounds fun.
The Pornoverse – the alternate universe where adult movies are set. All the women are beautiful, all the men are well-endowed, everybody is always eager for sex, and nobody has ever heard of STDs. Downside: Most people talk and act like idiots most of the time, and where’s that stupid music coming from? But that’s all right. I could gladly spend my whole life on the planet Barely Legal!
The Discworld for me too. Specifically Ankh-Morpork. And if I can have my namesake’s life, then fair enough.