i would say magnetos the best but he has a major flaw no one is concidering... that helmet is his down fall. if rogue could get close enough to him to use her power on him thenshe could use his metal controling powers while he is in his weak state and crush his head with his own helmet. now that would suck!
I hope i understand this thread right...it's the GREATEST, not the most powerful or the most popular, huh?!
I'd say Prof. X, Cyce (though i can't stand him) and Storm are the greatest. Those three are paragons of what it means to be an X-men/women.
My most treasured x-men are Nightcrawler,Emma and Storm.