To make a fight between the Justice League and the Avengers more dynamic, we'd have to replace Superman and Hulk with other important members. Hulk on the Avengers is pretty much the main loner, he could be replaced with Wolverine. On the JL, Supes is pretty much the team leader, without him, we need another with the same ability to inspire and command, Wonder Woman technically could, but she's primarily depicted as a feminist which would make it difficult for her to inspire her three male comrades, but she's already on the team so that point's moot. Steel is pretty much the DC version of Iron Man and, having himself been inspired by Superman, it wouldn't be much of a stretch to supplant the man-in-blue-tights with the man-in-stainless-steel-armor.