I'm not a big fan of the Fantastic Four, but I don't hate them either. The movies weren't terrible, and quite honestly they could have been longer.
Fantastic Four is reboot is scheduled to be in theaters in 2013, here is who I would cast.
Matt Damon as Reed Richards
Damon just fits to me, I think he is smart enough to pull off the role. In the Marvel universe, nobody is smarter than Reed Richards,and I think Damon can succeed in that kind of role.
Charlize Theron as Susan Storm-Richards
When Jessica Alba was playing Susan, I didn't really like the character, she almost seemed just fake to me. I like Jessica Alba as an actress, I just don't think that role was for her. I think Theron could play the role and make the character seem less corny.
Bruce Willis as Ben Grimm
I tried to find somebody else, I really did. But Willis is the Ben Grimm, and that's just all there is to it.
Mike Vogel as Johnny Storm
He fits... and that is all.
Mark Strong as Victor Von Doom
The guy fits! I almost casted the guy that played Sabertooth in the Wolverine movie. But Mark Strong is in my opinion the perfect choice for Victor Von Doom.