1. Red Bee versus Killer Moth
I picture a LOT of slapping. Followed by making up and shopping for leggings.
2. The Inferior Five versus the Secret Six
I have zero doubt that the IF would beat the tar out of SS, even if only by accident.
3. The Legion of Doom versus the Legion of Super-Heroes
I assume LoD would win, but only because the Riddler would find some loophole in the Legion's Constitution.
4. Mogo with Mogo
Naturally, they'd be fighting the Planet of the Apes.
You're welcome for that.
5. Gleek with Zook
GODS, I hate space-monkey-things. Maybe they would hijinks each other to death.
6. The Falcon and the Vulture versus Hawk and Dove
Before you bet on the heroes because they are 'super', remember that they can't fly. Air superiority, baby.
7. The Octopus versus the Shark
Well, sure, one is a hyper-evolved killing machine with super-telepathic powers and the other is an escaped convict with an open fish tank in his floor. But, hey... don't underestimate the power of tentacle hats and self-delusion.
8. The Phantom Stranger with Secret Squirrel
How they missed THAT opportunity during the DC/Hanna-Barbera crossovers I will never understand.
There's room for two MORE to make it a Top Ten list; what are YOUR suggestions...?