If... Holyfield had retired (permanently) after the first Tyson fight? Foreman quit immediately after he knocked out out Moorer? Hagler had been awarded the decision vs Leonard? Salvador Sanchez had lived? Castillo had got the nod over Mayweather in their first fight? The IRS had not forced Joe Louis out of retirement? Edwin Valero had lived? :think
The only ones that I think would've radically changed in the eyes of serious boxing fans would be Valero, Sanchez and Mayweather. I do think the first two would've gone on to even more with success and Mayweather would be a little bit more tolerable and more likely to take on bigger, more dangerous challenges. But, maybe not on that last one, now that I think about it. Why not the others so much? I just think serious boxing fans don't give or take all that much for things like Joe's comeback or George's lackluster reign as the lineal champion way past it or Holyfield's mostly missed marks after Tyson. I think also that people have a strong opinion on who won Hagler/Leonard no matter what the judges would've said and Hagler was pretty much at the end anyway, I feel, though only he knows for sure.
A little better. No different. Somewhat better. Probably worse. Considerably better. Exactly the same. Hard to say.
For me, the problem is that it even went to a decision. Marv's reputation took a hit when Duran went 15 with him, and it took the Hearns destruction to absolve him of that stigma. (Al Bernstein even referred to the match with Duran as "a loss" when Hagler stopped Tommy.) When the final bell rang ending SRL-Hagler, questions raised about what happened with Duran were guaranteed to resurface no matter how the judges voted.