omar's pretty fantastic. I saw the mars volta live, and it was one of the most incredible things I've ever seen. They had recently lost their drummer, and had someone replacing him, so rather than play their studio songs they did an improv set. I can't describe how awesome it was. If you listen to their studio albums, you might be interested to know John Frusciante (of red hot chili peppers) plays on 2 of the albums (the 2 newest, francis the mute and amputcture i believe).
As to the original post- I really only like Clapton and SRV off the original list. I can't stand U2, and think Hammett is very talented but just not quite in line with my music taste. What I like about clapton isn't really something I can describe. His playing just brings about emotion, I think Bell Bottom Blues is my favorite (I would add this to a "if you dont like this track, you don't like clapton" list), but the Key to the Highway jam with Duane Allman on the Layla album is probably one of the best guitar jams I've heard. It's just blues guitar at its best imo.