Seriously though, to answer the OP, not really. I mean there really isn't any difference between a Marvel/DC crossover and a fanfic on the internet. Neither one has any real or lasting consequences on either universe. As Jude pointed out, the whole story is calculated so that no one character looks better than any other character. If DC and Marvel ever had an actual story that featured lasting (albeit temporary) changes to their respective status quos, then yeah, I would read that.
You remember when they did the Access crossovers? They created this character, Access, to be co-ownedby both companies, so he could appear in either's books. And they made a big desk out of "when this crossover ends, not every character will be in their own universe!"
You know, saying in interviews and shit that they wanted to see about trading characters, like Daredevil goes to DC and Nightwing goes to Marvel. Man, 1990's/early 2000's me was all kinds of excited about that prospect. This would open untold doors of story possibility, it might be a new era of awesome....
And nothing. I don't think Access has been used since. And thus did Young Simian learn about "bullshit marketing hype".