>Captain America
Not him, but his buddy:
youtube.com/watch?v=HVJGh51wR7k
>Iron Man
youtube.com/watch?v=Uctu1e353os
Or, if it has to be an original song
youtube.com/watch?v=D5lmDMcmW6c
>The Avengers
youtu.be/8VGJGXMUhmc?t=1m4s
Another fantastic recent one:
youtube.com/watch?v=Q4uoNAFfvKg
It's not so much that soaring orchestral themes don't exist anymore. Listen to "Arrival to Earth", "He's a Pirate", "Flight", or for more percussive examples, "World Engine" or "Rise". There's plenty of examples, once you go looking for them. The problem is you have to go looking for them.
Look at the opening credits of Tim Burton's Batman:
youtube.com/watch?v=38lWxFNzCas
And of Donner's Superman:
youtube.com/watch?v=Rk1aQx9hTaE
Now here's The Dark Knight:
youtube.com/watch?v=yf8Ey1ZHIGo
And Man of Steel:
youtube.com/watch?v=Zs8hGVxWkFE
90% of why superhero movies seem to no longer have iconic scores anymore is the music is never allowed to breath and represent itself. And 90% of that is that movies don't have opening credits/titles anymore. If you put "Master of the Mystical End Credits" over some trippy montage with actor names and company logos, boom, that's an iconic and memorable opening credit scene. And suddenly that Pink Floyd mashup becomes "the Doctor Strange theme" and you can play it over a scene in Avengers 5: Age of Cashgrabs and people know that Strange is about to show up and do something magical. Chop the mid credits sequence from the Winter Soldier out, put it at the front of the movie, boom, memorable opening credits scene.
Remember how amazing the first 8-ish minutes of Watchmen was? The logos, a surreal scene of a super strong old man being beaten and thrown to his death by a faceless goon, and then Bob Dylan over a montage of the history of this alternate universe. It's a gold standard, and few movies really do that sort of thing anymore.