Having the Joker in your rogues’ gallery is a strong opening hand. IMO, Bats at least has the single best villain. Penguin, Riddler, Catwoman, Two-Face, Poison Ivy etc are all pretty iconic too.
Superman’s is pretty weak in comparison. I suppose there’s Luther and Braniac, but they stop being iconic after that.
Spidey is strong. Green Goblin, Doc Oc are probably the standouts.
I don’t know enough about X Men. Magneto? I'd argue if I can't name them off the top of my head, they're probably not that iconic.
I think it’s between Bats and Spidey.