WAY too many directions you could go, and you have to remember that some of these wouldn't "fit". And in some cases, as part of a band format one guy might shine, while another is just an awesome musician who can play anywhere, anytime, with anyone, no questions asked, studio or live, rehearsed or improvising.
My guitar list would break the bank before you even decide what you want for a song lineup! Do you tell John McLaughlin or Jeff Beck to sit down and shut up? And what about Carlos Santana, Chet Atkins, Steve Howe, Jimmy Page? The list could go way into the night. When it comes to rhythm guitar, though, I'm going with one guy: Freddie Greene, who played for years with Count Basie. Yes, I would tend toward jazz/blues-oriented guys, as their improv tends to be second nature.
Chris Squire did a solo during the 1979 Yes tour that was amazing, but if you said it meant leaving Stanley Clarke and Jaco Pastorius at home, it would be one hell of a tough dilemma.
"Drum" means two names: Gene Krupa and Buddy Rich. Oh, and Randy Jones (played a long time with Dave Brubeck). And throw in whoever happens to be playing for Spinal Tap, knowing you'll have to replace him soon...
Keyboards, wow, very tough call. Too many possibilities.
For vocalists, you're leaving a helluva lot of amazing females off the list
Another vocalist I would have to include: David Clayton Thomas.