Always a fun topic. I put this list together some time ago. My top 21. The first is my all-time favorite, with the last being my current favorite. I've seen most of these guys live at some point or another.
Gary Moore - 1983
Joe Perry - 1978, 1984, 1985, 2003
Jerry Cantrell (never saw live)
Zakk Wylde - 2005 with BLS
Tony Iommi - 1980, 1981, 1984
John Sykes - 2001 with Thin Lizzy
Michael Schenker - 1977 with UFO
Jimmy Page - 1985 with The Firm
Slash - 1991
Eddie Van Halen - 1979
Stevie Ray Vaughan - 1985, 1986, 1989
Randy Rhoads - 1982
David Gilmour (never saw live)
Jack White - 2005
Paul Chapman - 1979, 1982 with UFO
Alex Lifeson - 1977, 1978, 1980 (twice), 1981, 1982 (twice), 1996
Joe Satriani - 1990
Robin Trower - 1985, 1987
Billy Gibbons - 1980, 1983
George Lynch - 1985
Joe Bonamassa - 2006, 2007 (twice)
Gibson 60th Anniversary 1959 Les Paul Reissue, Gibson LP Standard Faded CSB, Gibson Gary Moore LP Standard, Epi Joe Bonamassa GT LP, Epi Zakk Wylde LP, Dean Michael Schenker Flying V, Jackson Randy Rhoads V, ESP/LTD George Lynch Kamikaze, EVH Striped Series R/B/W, Fender/Squire John 5 Telecaster, Fender Joe Strummer Relic Telecaster