I personally find a lot of the actual scores (not necessarily the main themes) unmemorable. If you think back on scores for films that were written some 40-50 years ago, there were a lot more distinctive tunes for each character or scene. Now it's more like incidental background music, almost trying not to interfere with the film itself but to blend in without being noticed. But the scores in previous eras did stand out much more.
For example, the early James Bond scores in the 1960s by John Barry were much more distinctive. If you take something like FRWL, Goldfinger or Thunderball, each part of the score is very memorable. For FRWL, you have the gypsy fight scene, Bond takes the Lektor (which became the "007" theme), etc.
With other composers like Max Steiner (King Kong, Gone with the Wind), Maurice Jarre (Lawrence of Arabia), Jerome Moross (The Big Country, The Valley of Gwangi), Ennio Morricone (The Good, the Bad and the Ugly), John Williams (Star Wars, Superman, ET etc) to name but a few, they all write distinctive melodies throughout the score for different scenes, each of which are memorable in their own right. They don't seem to mind that their tunes stand out, almost to the point of potentially overwhelming the scene.
In fact, Steven Spielberg changed the whole flying bicycle sequence in ET to fit John Williams's score, and now you always remember the scene in conjunction with the music.
I find it hard to remember most of the scenes and associate it with any particular music for the Marvel movies. It's almost reminiscent of how the later Star Trek series had more incidental background scores that didn't stand out as much as the scores for the original Star Trek series. It was as if the original Trek scores were seen as old fashioned and overly dramatic. But I remember these far more than anything in TNG, DS9, Voyager or Enterprise. And that's how it feels with the Marvel movies, as if they don't want their scores to seem old-fashioned and potentially "cheesy", but more modern, which then translates to more generic and background incidental and unmemorable.
Why isn't this a thing yet. Fox, darn you, let those rights go.
t:
Ultron was a complete and utter joke in this movie.
