I hope they can get Fantastic 4 working, but I kind of doubt it. The comics always felt a bit dated and corney to me as a kid - in the 80s when we were getting The Dark Knight Returns and Watchmen, F4 still felt like it was stuck in 1962.
They did get more interesting when they went down the path of Reed being kind of evil - it turns out he exposed them to "cosmic rays" on purpose, and Ben Grimm is not happy finding out about that.
Needs lots of setup though - would have to be at least the 3rd F4 movie.
X-Men on the other hand could be gangbusters. There are a ton of great stories that either haven't been touched (for a movie) yet, or could/should be re-done better (Phoenix).