Well, in a fight, I think with his powerset, he would wipe the floor with the X-men, but based on who I believe is "better", who I like more, I would say X-men. There's many more of them, all with their own stories, powers, complications, etc. Also, you never know if they're going to win the fight. With Superman, it's all about him so it's a 99.999% chance that he's going to win the fight. It's not as interesting.