Why waste your time? I'm going to get right to it. I have a feeling you'll either really like or dislike this fancast.
Reed Richards: Lee Pace
If you know me, you know that I'm a Pace fanatic. I'd cast him a million times over in everything I could because I think he's just that fantastic of an actor. I've wanted him as Daredevil, an older Spider-Man, and now Reed Richards.
Sue Storm: Katrina Bowden
Bowden is definitely on the rise and she packs quite a bit of comedic talent and enough genuine sincerity to really hit home a charming character. It'd be wonderful to see her take on the independent Sue Storm and add depth and character to one of comics finest leading ladies.
Johnny Storm: Ben Barnes
Barnes has sort of disappeared from the public eye, lately, and even though he was quite a hit with the ladies as Prince Caspian in the Narnia movies, I'd like to see him take on a role he can have a bit more fun with. I think Barnes is an actor that, when let loose, he could really surprise a lot of people. The only issue with his casting is that he is older than Bowden (who, in the comics, is Johnny's older sister), though I think that Barnes can play younger and Bowden older (even if it is just a year's difference).
Ben Grimm: Bruce Willis
An obvious fan-favorite, Willis is no stranger to comic book films (Sin City, RED) and to see him have fun with Ben Grimm could really be the tie that brings the whole family together. Normally, I'm against doing a major Hollywood player in fan-fics, but I've always been a fan of Willis.
Victor Von Doom: Jean Dujardin
Now, I'm aware that Dujardin isn't the strongest English speaker at this point, but I would have hopes that by the time my kind of Fantastic Four film would be made, he'd be fluent. He's an incredibly diverse actor and while he's known for comedy, I'd love to see him take a darker, more dramatic turn a-la Jim Carrey/Robin Williams. Obviously, Doom is a staple in the Marvel Comics world, and I'd love to see what Dujardin comes to within his Latverian castle.