Re: Avengers a culmination of Marvel history (including 616/Ultimate/etc.)
-Thor: Sleeveless or not, Thor's look is heavily based on the 616 design, with maybe a nod to the Ultimate version when he takes his cape off.
-Hulk: Not much to say here. 616 Hulk has been green for most of his history, while Ultimate Hulk has mostly been shown to be grey skinned.
-Iron Man: Based directly on 616 art.
-Black Widow: Black catsuit and stingers. both are 616 staples of the character.
-Loki: The green/gold motif, the huge horned helmet.
-Nick Fury: Based entirely on Samuel L. Jackson.
-Hawkeye: Again, the suit is pretty much a direct translation of Ultimate Hawkeye's uniform.
-Captain America: Arguably inspired by the Ultimate version, if only because it has some noticable design change from the classic version.
Forget about Jumping the Shark, now you have: Pushing the Apokolips!