5. He's Marvel's Superman Analogue
Fiction is teaming with characters that are essentially clones/analogues of DC's Superman - and why not? It's a formula that works; Handsome, super-strong, super-fast, super-durable, able to fly, wearing a tight outfit and a cape. It could be argued that Apollo (Wildstorm), Supreme (Image), Mister Majestic (Wildstorm) and Prime (Malibu) are all based on Superman in terms of power set and appearance - and there are more - and Sentry is just about the closest thing that Marvel have to the man of steel. There's an argument for others, like Blue Marvel and Wonder Man, but neither pack the punch of the Kryptonian from DC Comics. Aside from having a completely different personality (and a few extra powers), he's the superhero archetype and Marvel/Disney could do a lot worse than bringing a character like that to the Marvel Cinematic Universe.