I think the magic part of U2 is the live performance. I've never been a big fan of their songs, but when I put one of their concert DVDs on the player and turn the home cinema to 11 I'm mesmerized. The newest shows are a little too BIG, but still....
When U2 started to rise, there were few, if any, singers who had such cruel intensity combined with musical vibe in the voice as Bono.
And minimalism is very, very difficult. U2 has well succeeded in sticking to their basic sound. The arrangements are barren as the Irish hills.
In a way the band is a one trick pony, but all the bands that have become really big, are such IMO. Performers with variation and risk taking never fill stadions, only arenas.(OK, this is from the point of view of a scarsely inhabited country. I guess in London or LA you can fill a stadion with a " See the quills of a female hedgehog grow"-show).
And maybe there are exceptions..David Bowie...not a band...