ben 10 rules
he will beat superman because he has over a million aliens
Superman easily. He is much stronger (physically) than any alien in Ben's watch. Not to mention that Ben doesn't have an alien he can turn to that even moves at half the speed of light while Superman is capable of exceeding the speed of light and has escaped black holes which requires FTL speed. Not to mention he is far more durable than any alien in Ben's watch since he did withstand a supernova at a very close range and didn't even sustain a visible injury. Let's not forget that Superman's heat vision is hotter than the Sun and Earth's scientists couldn't measure its temperature however, they can measure the temperature of stars. The only way Ben can win is if he manages to gain full control of Alien X so that he can use his reality warping. But nothing is stopping Superman from effortlessly blitzing Ben before he can even think of changing from his human form. Hell Superman could use his insane speed to get to Ben before he can even think and he can just crush the watch along with Ben's wrist.
@t3h_bash: Alien X takes way too long to make a decision, in that time, Superman with his super-speed would have done something so unless Alien X is under Ben's complete control, he has no hope with any of his aliens. Ben could scan Superman but that doesn't make much of a difference. Superman could always blitz Ben before his brain can even process a thought. And even if Ben could transform into Superman after scanning him, he would still lose. Ben isn't used to moving at FTL speeds nor is he skilled at using Superman's strength and heat vision. Superman being more experienced would take advantage of that quite easily.