This is an insanely difficult question. It might be Paul McCartney when I saw him at Yankee Stadium. I'm not a fan of huge shows like that, but he played for about 3 hours and Billy Joel came on for a rendition of 'I Saw Her Standing There' during the first encore. Anytime I've seen Coheed and Cambria has been mind blowing-ly great, both from the music, and how into it the crowd has been. I lose it during their shows, and just go nuts which makes it a lot of fun. Another great concert was Jeff Mangum, that is another contender for the best show I have ever been to. That has a lot of cultural significance going for it (for me at least), and was a transcendent experience. I wrote all about that in this post. Honestly, it's probably a toss of between Paul McCartney and Jeff Mangum.