^ I think you're glossing over and trivializing the extent to which Avengers delved into the characters. It was a highlight of the film without question, and I think you're also missing the fact that the action itself was a method Whedon used to explore that depth. Every conflict in the movie up to and including the climax was relevant to each characters sensibilities, and the climax itself reflected their cohesion and growth as a team. The easy way out would've been to show the Avengers battling Loki and his cronies endlessly & aimlessly for 2 hours, but such was not the case. Taking the action at face value is missing the message, to a degree.
Otherwise, your conclusion isn't unequivocally true in the least. Watchmen was a damn good character study, but as a film, I don't think it holds a candle to the likes of action-driven films like Die Hard or Terminator 2. You can't shoehorn movies into boxes like that, because for every one example that you think illustrates that point, there are dozens of others that would refute it.
With all that being said, I do agree that Spider-Man 2 was a better film than Avengers.
Notice I said a
well executed character study. Snyder's execution wasn't close to Cameron's on Terminator 2 or Spielberg's on 'Raider's' or Lucas on the first Star Wars film. I would say Whedon and Raimi executed their stories the same. Both were extremely well executed. I'm not bashing The Avengers. I think Whedon nearly perfected what he was trying to accomplish. Same with Raimi. However, Raimi attempted something deeper and something easier to get in depth with because he has one protagonist.
And how are all the action sequences deep character moments?
1. Loki vs SHIELD- We learn Loki is badass and pissed off at the world and plans to destroy it. We learn SHIELD is outgunned and Fury is desperate for something or someone to stop Loki. That's what you learn about your character's in that action scene. That's mostly just plot development with little hints at the characters. Certainly not deep character development.
2. Cap vs Loki(and Iron Man at the end)- Again, Loki wants to rule the world. Cap stands up against him. Cap's got balls and heroism running through his blood fighting a god he doesn't have much of a chance with. Nothing out of the ordinary of a typical superhero story there. Nothing very deep. We learn IM is full of himself with his dramatic appearance. All of this are little moments that anyone who saw the previous films would know. Its simply re-introducing the characters. Its not bad, but certainly nothing to write home about as far as character development and depth goes.
3. Thor vs Iron Man(and Cap at the end)- Thor and IM don't fear each other, nor do they respect each other, yet they have at least a little bit of respect for Cap. Again, nothing bad, but nothing extraordinary either.
4. Thor vs Hulk- These guys are strong. Banner can't control Hulk. Thor must somewhat respect Banner because he tries to reason with him. Again, not bad, but nothing particularly deep.
5. Black Widow vs Hawkeye- This has the second most depth in an action sequence in the film. Two former allies, close friends, possible love interests, fighting 'to the death'. However,its not nearly as dramatic as it could be because Hawkeye is simply being controlled. No drama on his end. The drama comes from Black Widow because she knows what she's doing. This is brought up a few times in the film. It could have been expanded on, but this is a big film with a lot of moving pieces. Its understandable why it wasn't.
6. Cap and Iron Man against Loki's guards/ fixing the hellicarrier- Cap and Iron Man are heroes. They put their differences aside and team up to save the day. Iron Man is smarter than Cap in technology. Yeah, again, nothing bad, but not some great character moment amongst the action.
7. Final battle- Cap's the leader. Everyone sets aside their differences to work together to save the world. Banner randomly can control The Hulk even though earlier that day he couldn't. Iron Man can lay himself on the wire and sacrifice himself. Iron Man does have a big character moment in this action sequence for sure. However, no one else really does. Sure they work together to save the world, but it was pretty random. Black Widow and Hawkeye work for SHIELD and work for Fury. We can assume they were going to be team players from the start. Cap and Iron Man showed during the hellicarrier that they can work together. Thor and Hulk come together with everyone else at the end. Hulk partly due to Tony's speech.
So overall, yeah there are a few little character moments in the action, sure, but aside from Iron Man's sacrifice, Whedon didn't have any huge character moments or deep character statements in the action scenes. He did not 'explore and get to the depth' of these characters at very great lengths in the action sequences. The scene he dives the most into the characters is when they are bickering with each other and even that is mainly a plot point to show Loki's control and influence over the team leading to an action sequence.
Spiderman 2 dives into the psychological aspects of its hero and really lets us learn who the character of Peter Parker is. Obviously its easier to do that with one hero. 'The Avengers' IMO, is about as good of an 'origin' Avengers film that we could get, IMO. The nature of 'team building' stories means you can't have as much as depth for each character because you've got to get the team together first. Avengers 2 can and should dive deeper in its character's and Joss Whedon knows that, hence his comment about how making Avengers smaller and more personal being the only way to 'top' the first film.