This is a good film but they've taken a lot of liberties with the Death of Superman storyline from the comics. I understand that it isn't meant to be simply a visualization of the comic but it still should hold more true to the original story. No Justice League members, Super Girl, or additional superheroes are present. There aren't four new "Supermans" like in the comic, only a clone created by Luxor.
Another complaint is the voice talent. Tim Daly, Clancy Brown, and Dana Delany all did amazing voice acting work in Superman: The Animated Series so I expected them to reprise their roles but if not, have sufficient replacements. Neither can be said as their replacements are poor in comparison. Baldwin sounds much more like a whiny Peter Parker than the Man of Steel and Luxor's voice doesn't command the respect and attention Brown's did.
That aside, the action is really cool and the film is well animated. Explosions and lighting are look very awesome and realistic. The Doomsday/Superman battle scenes are very epic and easily the best part of the film.
I would rent this before you bought it unless you are a total diehard Superman fan who loves everything. If you aren't rent it or watch Mask of the Phantasm