Unfortunately, Fantastic Four falls a bit flat. That casting is part of the problem. I thought Chris Evans was funny as Johnny "Torch." However, Jessica Alba as a scientist? I'm sorry, that's just casting so against type that it doesn't work. There's also no plot or emotional depth. The film tries to add some morality with Ben Grimm (Michael Chiklis), but it just seems superficial (an the silly orange costume doesn't help).
The real problem is Julian McMahon as Victor Van Doom. I've always said a good movie needs a compelling villain. Van Doom's just a horrible, superficial villain. His only motive appears to be the lust for more power - so boring and cliche. He also has some of the corniest lines in the movie. For example, during the middle of the climatic fight scene, when zapping Jessica Alba with lightning, he says "Susan, you're fired!" That really breaks the mood and tension of the scene.
It's probably worth watching Fantastic Four once if you like action movies, but this isn't a keeper.
Overall, Fantastic Four: Rise of the Silver Surfer is better than its predecessor. The acting, effects, and plot are all a step up. The movie also has more memorable and emotionally poignant scenes (such as when Ben and Johnny sit in a bar discussing how they would spend their last minutes, Ben scaring the bear away...).
I'm still not crazy as Julian McMahon as Van Doom - and he still says corny lines in the middle of battles - but he's not so central to this movie. On the other hand, the Silver Surfer makes for a much better villain - mysterious, cool, and powerful. I like the end - a bit of The Day the Earth Stood Still (Two-Disc Widescreen Edition).