Even in the Harry Potter universe you could still end up being a muggle, so that would be pretty pointless. If you could ensure starting life out again in hogwarts then yeah it would be a top choice.
As for middle-earth, there are only a few people who can use magic and I'd like to maximise my chances of having magic/talents beyond human capability if I get to pick a universe of my choice.
I'd probably pick the Star Wars universe as the force flows through everyone, so you probably have a pretty good chance of being Jedi/Sith, and even if you don't at least you can train yourself to become a bounty hunter or something.
On another note, the Sherlock Holmes' universe seems pretty good as there are so many interesting cases to solve, unlike in this world where they all seem to be pretty obvious.
The pokemon universe has pretty much no faults lol - you get what you expect.