I think you guys are severely underestimating Sinister. Granted, I think Superman probably ultimately wins, but Sinister is VERY powerful. He's shown CL100 strength and even greater durability. He's shown pretty powerful energy projection and very strong telepathic defenses. I think with prep, he could steal at least a few victories from Superman. The big key here is that Superman is just as incapable of beating Sinister as Sinister is of beating Superman. Sinister has shown invulnerability to everything short of psionic or molecular attack...or Scott's optic blasts.
So, in a 10 fight series, I'd give 3 to Sinister.
He easily manhandled Colossus and a dogpile of X-men at once and threw them all back with incredible ease in the finale of Inferno. He also showed incredible speed in X-men 221 when Sabretooth surprise attacked him and Sinister caught him midair, held him up with one hand and slowly started choking the life out of him to make a point. Havok blasted him and he instantly healed. Cyclops blasted him to dust and he was back some time later. X-man telepathically assaulted him (in an X-force crossover) and Sinister not only reversed the telepathic attack, he amplified it to take out both X-man and the entire X-force team. He shoots energy blasts in just about every combat appearence, most notably against the High Evolutionary, who he completely owned (something Apocalypse himself was unable to conclusively do)
So don't underestimate him. He's better than you think.