I hear what you're saying. As a long-time comic reader, I couldn't imagine an Avengers movie that didn't climax in a massive battle scene. The Jack Kirby-era Marvel comics were famous for that. And ever since Whedon was announced as the director, he's been vocal about his love for Jim Starlin Marvel comics - which added even more sci-fi to the mix. If you were surprised by the ending of the movie, or saw it as a trope brought on by Transformers, then I can see how you'd be let down.
Personally, I'm looking forward to something like this in Avengers 2:
