Bayonne Bleeder Chuck Wepner's challenge of Ali was the inspiration for Rocky. And Stallone did take quite a bit from Smokin' Joe Frazier like fighting out of Philadelphia, running the stairs at the museum, and punching sides of beef as Joe did when he worked in a slaughter house.

I think the Gatti-Ward fights were the most like the Rocky scenes. Guys getting hit so much and still fighting back that it was unbelievable.

Rocky III came out in 1982, and they created a monster of a fighter in Clubberlang.
When Iron Mike Tyson turned pro a few years later in 1985, and was demolishing Heavyweights in 1986, he was way more intimidating than Clubberlang, his fights were more destructive than Mr.T's screen fights. It's amazing because it was so real and so riveting, not a choreographed film-fight.