I recently saw Fantastic Four, which got fairly bad reviews. It was actually a fairly good movie. There were definitely weaknesses, mostly in the characterization of Dr. Doom. Victor von Doom, of course, is one of the great all-time supervillains,* and he has to be done right; getting him wrong is like getting Magneto wrong -- it throws everything else off. Julian McMahon was actually a fairly good choice for the role, but (1) Von Doom has to be written as brilliant (second only to Reed Richards himself), and this really didn't come across; (2) while moving Von Doom from dictator of Latveria to corporate industrialist probably made the script a bit easier to put together, it lost something of the characterization. A little more benevolent-but-ruthless Latverian-gypsy dictator and little more scientist would have improved the portrayal. For the rest, it was just the trickiness of developing five major characters adequately; and, while this didn't leave much room for any sort of profound plot, they did reasonably well.
* I suppose that if we were to make a list of the greatest comic book supervillains of all time, Doom (Marvel) would only have rivals in Magneto (Marvel) and Luthor (DC). Magneto is probably the most popular; Doom has the formidable track record and (very easily) the best success rate; Luthor -- well, he's Lex Luthor, enough said. All three, interestingly enough, are stupendous supervillains in part due to their good side: each of the three clearly has a noble streak, each had the initial makings of a superhero, but each is flawed by an overwhelming pride and thirst for revenge. The worst is always the perversion of the best.