QUOTE: Superman vs Mephisto

That could be awesome.  Done by either JB or Alan Davis (never seen a Davis Mephisto before).

Some good answers here, folks.

You're going to think this is really stupid now, but as a kid (and maybe even into my early teens), me and a friend used to write down names of superheroes and supervillains on bits of paper. The superhero bits of paper would go in one hat, the supervillain bits of paper would go in another hat. We would then pick a bit of paper from each hat in order to come up with a match-up - we would then discuss it.

So, I might pick out Batman's name from the "superhero" hat and my friend might pick out "Electro" from the "supervillain" hat and we'd have a bit of fun discussing a Batman/Electro battle.

It was fun although we didn't do it often. Some real good match-ups came out of that game such as Martian Manhunter VS Man-Bat, Guy Gardner VS Scorpion and many others.

How about a matchup vs Ultron.  I liked the Sinestro option.  With any luck we'll be seeing that in one of the GL books soon.  I also liked the idea of vs Thanos.

Superman VS Ultron would be another action-packed story, if it were ever written.

Another one I'd love to see would be Superman taking on Dr. Sivana (can't recall that happening).

By the way, off-topic, but has Captain Marvel ever fought Solomon Grundy?

What about Superman vs. Captain Marvel (Mar-Vell) would cosmic awareness help even out the fight?

Also could Doctor Strange take Superman down? We all know about Superman & magic.