Originally Posted by xeno000
If more than one character having any power makes it cheap, then there ought to be only one super-strong hero, right? So by that rationale Thor shouldn't have super-strength, because Hulk beat him to it, though Thor's "god of thunder" weather powers are unique. (Storm should never have been created, though.) And Captain America just might as well not suit up at all because he's just another strong guy, albeit with a strength level that's far below the others. Bringing in Ms./Captain Marvel would be even more redundant since strength is one of her main shticks, along with energy blasts that duplicate Iron Man and Thor's powers. There should be only one Ant-Man, of course (though Wasp gets a bye because she has wings). And so on.
That were would be true if Thor turned into a big huge green guy, or if Hulk had a Hammer and could summon lightning. All those character you mentioned have very different gimmicks.
In Iron Man 3 you're literally going to have three people using the EXACT same weapon system. Rhodey makes sense in the movies being he's a pilot, and Stark wanted to bring him in on it anyway.
That said, I have yet to see anyone post a real reason why this should happen except it happens in the comics, and Fraction's Iron Man should be completely ignored because it's craptastic.