I do agree that there was a sense of ULTIMATE AVENGERS stuck attempting to please both of the "kiddie audience" and "adult audience" in many ways. But I think this was forseeable from the get-go. Anyone who makes animation in America is going to assume that children are likely going to eventually be seeing it, if not buying it or having parents buy it, seeing it on CARTOON NETWORK inevitably. Plus, the best animated projects try to appeal to both groups anyway, such as SHRECK, THE INCREDIBLES, and in some ways the "Timmverse" projects (B:TAS,S:TAS, BEYOND, JL/JLU).
The thing about THE ULTIMATES as they are written is that Mark Millar writes from an extreme point of view, and usually can only depict most characters from an extreme. And one of his flaws is that he has a hard time making a character looks sympathetic without either failing and creating a stereotype, or making the entire story ungodly depressing, much like the Pym/Defenders issue of Ultimates 2. The "stale aliens" plotline was lifted directly from Ultimates; just instead of having the Avengers fight NO threats and only fight the Hulk when Banner wants to give them "something to fight so they don't lose their funding", the film introduced the aliens early with the full intention of fleshing them out more in ULTIMATE AVENGERS 2 (at least that is the theory). Granted, that made the aliens stale here (and in general aliens tend to be stock, boring enemies when compared to supervillians), but the lack of supervillians was the fault of ULTIMATES. Even fans like me of the Ultimates usually tire of the team spending most of their time fighting themselves; only the second half of Ultimates 2 seems set to have bonafide villians.
As for extremes, not only is Hank a "wife-beater", but he viciously puts Wasp into a coma. There is no way to feel sympathy for a man who does that. Cap also spouts morals one minute and then suckerpunches people the next, leaving some to think he is a thug. Ultimate Hulk has no heroic tendancies whatsoever and is simply a monstrous cannibal. Ultimate Thor exists as the "ultimate hippie" as one of Millar's many voices who claims that "America is evil" in Ultimates. The point of extremes is that they will divide your audience if they do not agree. Millar is a Liberal, and like most liberals, he preaches to the choir. The makers of the movie likely wanted to stay out of politics and display an unapologetic superhero thing. While that takes a little away from Ultimates, it is fitting for Avengers (the only time the Avengers usually got political was usually when Cap, a WW2 vet who likely had killed dozens of Nazis over his career, would suddenly go pale if he had to justifiably kill again, even if said threat was worse than a billion Nazis). I DID miss some of that "connection" to the public that the Ultimates had, being media darlings. Iron Man had that for a few moments at least.
Overall, though, I enjoyed the film as escapist superhero adventure that, unlike Ultimates, isn't so busy trying to convince me of some political point that it is forgetting about the superheroics (even though I do like The Ultimates a great deal and anxiously await every late issue). It was supposed to combine a mishmash of both 616 Avengers and Ultimates and somewhere have a voice to its own and while it wasn't perfect, it was a bright spot in Marvel's currently shady animation history. Recall that this was their latest project since MTV SPIDER-MAN and the finale of X-MEN EVOLUTION. And surely it was better than past incarnations of animated Avengers as seen in AVENGERS: UNITED THEY STAND in the 90's.
I am concerned that instead of focusing on the remaining Avengers in ULTIMATE AVENGERS 2 or introducing Hawkeye (who DID show up in the second half of Ultimates), they are going with Black Panther to tie him into the Cap/Klieser thing. That may be interesting but I do hope the film is longer and delves into the other characters (it does seem Thor will be covered a little from what the featurette mentioned, at least). I do see where a sequal could be far better, much like X2 was a bit better than X-MEN was. And IRON MAN will naturally flesh out Iron Man a bit more, much like Superman and Batman in JL had their own series behind them, so they didn't have as much focus in the beginning.
And naturally if ULTIMATE AVENGERS 1 & 2 sell well, Marvel & Lion's Gate will make more (perhaps that is why their deal is for about 7-8 DTV's and only about half of them so far have been announced; they are testing the waters for sequals), which could be cool. If anime can make OAV series on their own Japanese comics, why can't we with OUR comics? This is a trend I want to see continue and improve, so I'm supporting it now.