First, the negative: They failed to salvage Doctor Doom. They COULD have -- there were some excellent plot possibilities -- but the guy playing him wasn't handed Doom lines, and perhaps just couldn't handle the role. Doom is DRAMATIC. He's a scenery-chewing, MAJESTIC, ranting, HONORABLE villain with grandiose plans. Unfortunately they only got pieces of him. The plan he had was, actually, quite a Doomlike plan. He just didn't have... DOOM in him.
Part of that's probably just the actor; to pull off that character requires a lot of stage presence so you don't look stupid. If he was about 40 years younger, Christopher Lee would be perfect. (Count Dooku from the Star Wars prequels was very much like Doom, actually.)
That, however, is the ONLY failing of this movie. And they get the rest SO VERY RIGHT.
The Silver Surfer is *PERFECT*. From his mysterious, cold, unspeaking entrance to his slow humanization to his final decision, he is visually, artistically, and emotionally The Silver Surfer, straight out of the comics.
The Fantastic Four are *PERFECT*. These are the Four as I remember them from the comics, especially the earlier years, when Johnny was still a wiseass, arrogant pain in the ass, Sue and Reed still figuring out how to deal with being The Fantastic Couple, and Ben Grimm stolidly soldiering along and mostly not complaining, no matter how much complaining he had a right to do. Of the four actors, Jessica Alba is the only one who doesn't have the perfect LOOK (Susan Storm was more model-gorgeous than blonde-cute), but even she *IS* her role. These actors either read the comics, or were coached by people who intimately understood those four characters. (this does make the failure to make Victor Von Doom correctly more of a mystery; how you can get the Four note-perfect and completely fail to understand Doom, I don't know.)
The reimagining of Galactus... excellent. Much as I love him, our favorite Art-Deco Helmet-wearing giant would just look stupid on the screen, no matter who was wearing the costume. The cosmic force they depicted in this movie is much more awesome and terrifying, and convincing. (and we did get one nod to the original Galactus, in the shape of the shadow moving over Saturn)
Overall, this is an 8.5 movie. Very fun, pretty much family-friendly, and pretty well paced, too.