The Water bender before Kyoshi that got he's girlfriend taken by the face stealer that would be awesome!

Personally, I really feel like any previous avatar would have been a hell of a lot better than our current avatar, Korra. The older characters are far more interesting, and the stories that have already been established, can be expanded on. I think it would have been great.

Adult Aang would have been great, as it would be a continuation of what we've all previously loved, and it could only get better. As for Roku, that again, would have been a great story, as we already know the ending, but we could have started from the beginning. Kyoshi would have been great.....and she would have been a much better female protagonist. The water bender before Kyoshi was cool too! Also, Wan is a wonderful addition to the avatar family. His story was really interesting, had a lot of symbolism, and the story really should have been spaced out longer. His story is the first story which was great, but his story is so much more interesting than Korra's struggle to try to be spiritual and yada yada. Her story is boring in comparison.

All of them!!! :)

I would so watch it

Or Roku.

The Legend of Wan, why the heck didn't they do that instead of Korra.

It would be cool to have a show with one of those other avatars but Korra is my favorite avatar story :D