You all have some long lists for "best ever."
Mine goes like this:
1. Metallica - 1998(ish) in Atlanta. My dad's big into rock and metal music so we would go to concerts together. My second time seeing Metallica was the biggest and best show I have ever seen. I'm not much of a fan of theirs anymore, but I can still remember the feeling of awe and the energy and the lights and bombs and fire and intensity and everything else that came with a Metallica show.
2. Sigur Ros - 2006 in Atlanta. Simply a beautiful show in a beautiful setting (the art museum). The visuals on the big screens that accompanied their music created more of a story than just a music show.
3. Radiohead - 2005(maybe 2004) in Atlanta. Innovative. Exciting. Cogent. Not much beats a Radiohead performance.
4. Tommy Emmanuel - 2001 at Indian Springs. The best show I've ever seen by him. I heard him say a few years later that he felt so on fire that night that he played an extra 30 minutes of music.
5. Styx - Whenever the last City Stages was. Nostalgia at its best. My mom was a huge Styx fan, so I remember listening to their cassettes as a kid. Getting to see them live 20 years later was tremendous.