Captain America and Iron Man team up to battle the Red Skull and the unimproved Taskmaster as well as the Skull's Hydra forces. Steve thinks Tony never has a plan, and Tony thinks Steve is too rigid in his thinking, so naturally our heroes don't always get along, but in the end they have figure out a way to stop hordes of giant Cap clones that will help the Skull take over the planet. Fortunately Iron Man has a large green ace in the hole. I kind of figured this might happen, and it's a nice touch.
The CG animation is not much to look at. At least they don't keep taking their masks off every five seconds to make sure the audience knows who the actors are. I think these are the same actors from the cartoon series. It's the interaction between the heroes that carries the story. It's pretty fun, and have I mentioned I really like this Hulk, the one that isn't a child like monster, but can think and understand the world around him.
The Skull is still a jerk, and the Taskmaster's photographic reflexes strain credulity, even from a comic book villain. I mean, sure, he might be able to copy all the moves the various heroes he sees do, but he doesn't naturally have the strength that Spider-man would have to swing like he does. He'd tear his arms out of his sockets. Or he may be able to throw a shield like Cap but without the years of experience... he'd still need a lot of practice.
Anyway, if you have 71 minutes to kill this is a fun little movie. It's not great, but I've seen worse. Oh, and Cap's still not the first Avenger.