Interestingly, I wasn't even talking about Superman and Batman fighting each other but about them working together and them having to dumb down Superman. There was a time when they worked together but Superman clearly came across as superior because the writer didn't hold him back.It's about not telling a boring story. If Superman wins like he's supposed to, that's not interesting because it's exactly what we expect. It doesn't matter how powerful Superman is, this is likely to happen if they fight at all. I guess we should be thankful that hero vs hero, besides the "meet and misunderstand" thing, wasn't in style so many years ago.
But think of the amount of people who are likely to pay to see a 90 year old man beat prime Mike Tyson instead of the other way around.
I think now the expectation is completely that the writer will dumb him down and the average reader doesn't even think about what they are in their respective titles. If I hear about a crossover today, I have almost zero expectation that Superman will be operating at his top form. I fully expect that Batman will be. That is totally predictable. Today, the surprise would be if Superman was in top form and resolved a majority of the problem, physically and mentally, himself.
And I am glad there was a time when heroes met each other to work as a team rather than fight each other. For a period of time, whenever you had Superman and Batman team up, whether against Lex Luthor and the Joker or whoever, I (and likely Superman) was more worried about what Batman would do to stab him in the back than what the villains would do. I'd much rather get back to them being a team. In other words, "Batman Meets Superman" rather than "Batman versus Superman".