by 3dicebombers
An awful lot depends on which cards come up. Flash is not very powerful if Flash and Location cards don't come up.Aquaman is probably the best in a vacuum; putting cards on top of your deck is such great acceleration and is always helpful.
Batman, Superman, Green Lantern, and Manhunter (if you have him) are all very powerful if you can build your deck to trigger their extra power abilities, but you may not have access to the right cards to optimize them.
Wonderwoman is obviously only as good as the villains that come out.
Cyborg is pretty "meh" to me, both his abilities are okay but not amazing, and you'd really want to trigger both every turn to get good mileage out of him.
That's my analysis anyway, after quite a few plays. Overall, I don't think you can pick a "best" because of the variability of the lineup. My personal opinion is that Cyborg is the worst, however.