As a big fan of the Ultimates series, I had high hopes but low expectations for Ultimate Avengers the Movie. I was worried they would strip out much of the darkness and complexity that makes Millar's vision of the Avengers so interesting. The film was better than I had predicted, but still fell short of the high standard set by the comics it is based on.
The film pretty much rehashes some of the major themes and story elements from the first volume of the Ultimates. The plot has been altered somewhat, with new incidents and elements, so even if you've read the comics it is worth seeing the movie.
Let's spend a few minutes on the positives of the movie. The quality of the animation is excellent, and the film is visually engaging. Some of the characters are very well done also. The raging Hulk character is great, and his fights against the rest of the Ultimates are very entertaining. Too often animated superhero fights are too tame and abstract, which is not the case here. The Hulk attacks in a specific, graphic manner that makes you feel viscerally the pain the other characters are enduring. The Hulk works great in an animated context because he can crush tanks, etc. in a really exciting way that just doesn't work in a live action context. I think Marvel should put together a regular Hulk series that is more adult oriented and try it as an evening show rather than a morning cartoon. Captain America's confusion about modern life and his alienation and loneliness come across pretty well. One of the sweetest aspects of the Ultimates as a series I think is the relationship between Cap and the aging Bucky. We get part of it here, but it could have been even more developed. Finally, Nick Fury was done very well, both from a voice acting and character development standpoint. I would be interested in seeing a SHEILD series coming out of the house of Marvel alongside a Hulk series. Other than the characters, the movie also does a fairly good job of keeping the dark character of the series. There is quite a bit of realistic physical violence, from the Private Ryan-esque opening of the film through the Hulk nearly choking Giant Man to death. The human tension from the series, with characters that are really nasty to each other is there as well, though tamed down from the comic.
Now to the bad news. The studio clearly drew a line that this picture wasn't supposed to cross and it is drawn too close to the middle of the road for my taste. The Thor character while still being an environmental activist, doesn't really rail against the system to the same degree as in the book. The intra-team conflicts exist but the Henry Pym - Wasp domestic abuse issue gets left out. I found this particularly unfortunate as the ant attack episode from Volume 1 of the Comic series is one of the most realistically terrifying incidents in modern comics. The issue around the execution of the Hulk doesn't arise, and Fury is represented as less of a potential fascist / bootlicker than in the series. So, while the darkness remains, much of the ethical complexity has been washed away.
The film was too short, leading to a feeling that many things were rushed and the underdevelopment of many key characters. In particular, I would like to have seen more of Thor who is in the movie for a very brief period of time. Tony Stark, Henry & Janet Pym, and the Black Widow could all have been developed more. We don't really get much of why they do what they do or what is motivating them. The main plot suffers from this to a huge degree. The aliens that helped create a nuclear warhead in 1945 for the Germans are still hanging around in hiding 60 years later. Since they have what seems like completely invulnerable technology, one wonders why they have been hiding so long. Also, there is no attempt to give an indication of what the aliens' agenda is. Did they travel across the universe just to hang out on Earth? The Ultimates was a fabulous series that had more than enough material for a 2 1/2 hour project, but we get a mere 71 minutes.
Overall, if you are a fan of the Marvel Universe, and the Ultimates in particular, I would recommend seeing this film. It isn't as good as the comic books it is based on, but it's still worth the money to rent from the video store. If you aren't familiar with the Avengers, I would hold off on seeing the film until you've read through The Essential Avengers Vol. 1 as well as The Ultimates Volume 1. My fear is if you haven't read them before you see the movie, you won't be inspired by the movie to do so.