Became major players in these crossovers

Fear İtself

Age of Ultron

Secret Invasion

Dark Reign

Civil War

AVX

Its largely a case of Meh if the DC trinity came to Marveldom... We already have many Batman stand-ins, as smart and deadly or moreso. Wonder Woman has a power match or better on every team... Warrior-Amazon-Princesses are a dime a dozen. Superman might change some things tho - but could he still be Kryptonian? Is there a Krypton in the marvel universe... i suspect not. He'd be Strontian (like Gladiator) or an Inhuman or a mutant perhaps. Either way of course, his powerset is extremely formidable, but not unmatchable.

I don't think their presence would have changed much of the action or resolution to many of the crossovers. They're not significant enough in powers and skills to change things dramatically in the marvelverse - as teeming with monstrously powerful geniuses as it is.