From my experience, it's fairly easy to earn 200 reputation a day on Stack Overflow if you write a few decent answers. Meanwhile, it's incomprehensibly hard to earn 200 rep on Android Enthusiasts a day, even if you write 200 great answers.
I'd like to find out on which site it's easier to earn reputation. For example, comparing reputation leagues across sites could be a good method, but there's no easy way to do so (except writing a program that fetches all leagues and parses them), is it?
FWIW, the highest reputation on a single site is undoubtably Jon Skeet on SO. The second highest appears to have gone to egreg on TeX - LaTeX.