I know here on the site people like pictures to go with fan casts to make the read more interesting and insightful, but right now I am unable to upload pictures so I decided to just post a quick video instead.
EDWARD NORTON as DR. REED RICHARDS/MISTER FANTASTIC:
I enjoy Edward Norton's work and I think he can bring the smarts and wit needed to play Reed to the table.
CHARLIZE THERON as SUSAN STORM/INVISIBLE WOMAN:
Susan Storm is really the first woman of Marvel comics, and so I felt that an actress that was accomplished, talented and acceptable needed to be cast. Charlize can lend some much needed respect to the role and she could add a strong side to the character that is necessary. This casting is not really a new idea, but Charlize is just so perfect.
GARRETT HEDLUND as JOHNNY STORM/THE HUMAN TORCH:
From what I have seen of Garrett Hedlund he can play Johnny Storm, I felt he really would own the role just from seeing him in TRON: Legacy alone. He can own it.
KEVIN DILLON as BEN GRIMM/THE THING:
This is an out of the box idea from my end, and I am not completely sold on Dillon in the role though I do think it would be an interesting possibility.
CLIVE OWEN as VICTOR VON DOOM/DOCTOR DOOM:
Clive Owen is just a tremendous actor that can play this all powerful villain and leave an impression.
CLANCY BROWN as GALACTUS:
I don't need to explain this one, Clancy Brown would own.
DENNIS QUAID as NICK FURY:
I wanted to cast a famous actor as Nick Fury that would be big enough to really live up to the importance of Fury in the comics. Dennis Quaid really struck me. He is both likable and can be fitting for the role.
ELENA SATINE as NATASHA ROMANOFF/THE BLACK WIDOW:
Elena is a very talented young actress that could really shine in the role.