9. Rocky
Probably the most unbelievable thing about Rocky is that it doesn't draw any attention at all to the fact that it's based on a true story, given that this would surely give the film an even more pronounced inspirational appeal to fans. Though many have disputed throughout the years that Rocky Balboa's underdog story is actually based on the life of the infamous "Bayonne Bleeder" Chuck Wepner, the fact that Stallone settled a lawsuit with him for an undisclosed amount makes it pretty clear that Sly didn't come up with the story all by himself. Sure, some facts are different, but the core narrative is the same; a working class young guy who works menial jobs while trying to become a world-class boxer ends up getting a shot at the champ. Hell, Wepner even ended up having a boxing match against a wrestler once (as happens against Hulk Hogan in Rocky III). Even today, with the film's massively iconic status, most assume that Rocky completely materialised out of thin air into Stallone's mind.