Quote Originally Posted by Ansem/Sephy
The reason people like Sephy better is simple: even after Sephiroth goes insane, you understand his pain. You sorta pitty him.

And Ansem: Some philosopher king who goes mad, becomes consumed in Darkness and attempts to conquer all worlds, while trying to become, basically, God.What's there to pitty, Seph had reason to go crazy, Ans didn't, he's just wicked beyond reason.
Sephy went mad, was pretty much consumed by darkness, and tries to become one with the planet, which is pretty God-like if you think about it. So yeah they are similar, but I see no reason to pitty either one.
Sephy needed to be killed when he summoned Meteor to destroy the planet. All Ansem needed was a smack in the head so he would quit thinking the darkness were so cool.