Spidey - This one I'd say is pretty original just because he's part of the original "heroes with problems" Marvel ethos. For inspiration though I'd point to Robin.
Wolverine - Wildcat is probably the closest example, although since Wolverine started as a hulk villain you'd be better off citing characters like Cheetarah.
Captain America - Golden Age Superman
Iron Man - definitely Batman.
Really though the main source of overlap between the two franchises is Jack Kirby. His art style defined both businesses for decades and he's responsible for the New Gods as well as Thor which are both takes on each other along with countless other characters. Hulk - Solomon Grundy, Thanos - Darkseid, Asgardians - New Gods, and so on.