Razjah
Explorer
The problem comes in when we have such characters as almost ubiquitous. You've mentioned examples below. Drizzt is not The Greatest Swordsman Ever. Han isn't off the ability curve. Nor, for that matter, is Obi-Wan (unless you don't have Force access). These characters are not legends that almost define the setting. The PCs should be able to resemble and then surpass them given time and experience. But this doesn't mean the same should be true for everyone - normally not for setting-wide BBEGs.
I agree with this. In a D20 game, I think Han would be around level 8. If I make a level 10 character following most of his build- I better be able to do things he can't! As for Drizzt- awesome swordsman-yes. But he has met several characters who can match blades with him (notably Artemis Entreri). So PCs should be able to match, then exceed, his capabilities.
I do think game designers/authors try too hard to protect how awesome a character is in the world. Like the Tony Stark thing, if he is one of the top 3 smartest people alive, I think giving him a 20-22 is perfectly reasonable. Normal people are gifted if they have an 16. A genius with an 18. Going higher than that is incomprehensibly smart. But now we run into the problem of games not defining what an "18" means or "level 5" in the world.
Perhaps authors should follow this : if something is truly spectacularly powerful- Don't freaking stat it out! For example, I only give gods stats in my games where it is something like an E6 game where they walk the earth. I wanted giants to be a threat to Olympus, so the giants could gang up and kill the gods. If I was playing a supers game in the Marvel universe and the characters were "street level" supers, then I wouldn't even stat out Iron Man/Tony Stark. He is smarter than them, and as Iron Man he can take on the whole group and walk away with little to no damage.
Adjusting my original answer:
E6/ "Merely Human": Stark has a high (PC can't reach it ) INT score
Low Powered Supers: Stark has something closer to a 25 INT
Avengers: Stark has something like a 30 INT and an an ability to boost his smarts based checks periodically (for moments of brilliance)
We Fight Galactus: Stark has an INT of slightly higher than the highest possible I expect the PCs to achieve. They could pull this off, at the cost of all other abilities (Stark's only power is his brain, the suit does the heavy lifting).