Planned extermination of entire nations doesn't compare well to incidents like those mentioned on that wiki page. I don't think it compares at all. While you have some good points in your post, there is a question of scale, motivation, purpose... You are talking about the world not being black and white. Yes, there may be only shades of gray, but they do range from, say, close to white to almost black. Hitler, Stalin, Mao, they are close to black. Who, of the leaders of Europe today, can be compared to them?
And about extermination of entire tribes in Africa/America - these are real and horrible crimes too, no doubt. Leaders guilty of making/letting them happen are as guilty as Hitler, and they do deserve to be considered vicious and evil - which is the opposite thing to calling Hitler "just another leader". All evil leaders are leaders, not all leaders are evil leaders. What Hitler did was specific to him. Would, say, Hollande do the same? I doubt it.