Brad Wilson’s reluctance to see Superman Returns hits on a reason I prefer series over feature-length movies:
Smallville’s Lex is smart, devious, capable, and above all, not yet evil. The on-again, off-again friendship between Lex and Clark, and the tremendous loyalty that they have both shown to each other, makes the idea of seeing a fully-evil, hell-bent on destruction Lex a lot less interesting. The Lex of Smallville is a conflicted, emotional, sometimes unstable human being. The movie Lex has tended to be an unrelentless force of super-human evil, a character of less dimension and interest.
When you have 24 episodes a season, you can afford to develop characters in depth. And if you’re working with a mythos with nearly 70 years worth of comics, movies, and cartoons, you need that space.