Radiohead, because the influence they had on music was immense, their evolution of sound from album to album was huge. One could say the purpose of music is to evoke emotions, and Radiohead evokes emotion, not usually the ones you want, alienation, melancholy, tense paranoia; cold, hypnotizing, sprawling detachment is common. Radiohead gets in those weird crevasses and pulls it out; in that way they succeed far more than many bands do in understanding the connection between sound and emotion. Each album also seems to strike different facets of sound and meaning while staying utterly unique to Radiohead.
Having said that, I probably don't listen to them as much as the other bands, not because they're bad, it's because it's potent music and I usually don't feel like connecting with melancholy and tense paranoia on a daily bases, but they are the most talented on the list in my opinion.
I also can't argue with Iron Maiden, they're damn good.
