Why are Che Guevara and Christopher Columbus viewed as great heros?

I don't think of Columbus as a great hero. As far as Che, I probably don't know enough about him to have an opinion, but I think the reason people view him as a hero is that he really wanted to change things for the better. He was a revolutionary. I agree that being a m murderer really isn't something to admire though. And I'd have to say Che isn't one of my personal heroes.