Why not Green Arrow and Bullseye?

Or Hawkeye and the Human Target?

Those are 2 team-ups I'd love to see!!!

JB: "Raising what is, to me, the Eternal Question: why crossovers with characters who are essentially the same?"

Sure, they both shoot arrows, but JB, if you could pick any point during their careers, say, when Oliver Queen was still a rich playboy ... wouldn't that be an interesting contrast with Clint Barton, a performer from a two-bit carny, whose first name would never have been allowed in a DC comic edited by the late Julius Schwartz? 

Best crossover ever: "The Hunger". Which provides a set up of equal measures of like and unlike, to my mind. Both Galactus & Silver Surfer and Darkseid, Apokalips & the New Gods are so clearly cosmic Kirby, but at the same time Darkseid's villainy and the entire set up of Fourth Wolrd is far from the lonesome creation of Galactus and his herald.
Anyway, JB really created a story here that feels so right on o so many levels. And in the end it really doesn't feel like a croosover at all, which I guess is how it should really be, somehow.