Of the ones you listed, I suppose I'd have a tough time picking between Satriani and Petrucci. Kind of surprised you didn't list Eddie Van Halen, Jimmy Page, Jimi Hendrix, Alex Lifeson, Stevie Ray... they're all fairly "mainstream", and I'd consider them quite influential as well.
As far as lesser-known guitarists go, here are a few of my personal faves (in no particular order):
Steve Morse (formerly of the Dixie Dregs)
Scott Henderson (really cool jazz/rock/blues fusion player)
Scott McGill (jazz-rock, lately a bit more avant-garde)
Allan Holdsworth (incredible jazz-rock guitar and guitar synth player)
Shawn Lane (jazz-rock)
Terje Rypdal (Norwegian guitarist and composer who is basically impossible to classify)
David Torn (guitar "texturalist" and composer)
Bill Connors (jazz and jazz-rock)
Nuno Bettencort (rocker somewhat in the Eddie Van Halen vein, formerly of Extreme)
Kazumi Watanabe (Japanese jazz/fusion guitarist)
Steve Tibbetts ("texturalist" and composer, similar to David Torn)
Bon Lozaga (great fusion guitarist, also does some "textural" stuff, ala David Torn)
(I tried to post links to bios of most of these, but allmusic.com's links give phpBB indigestion for some reason. You can go there and search on them yourself if you're curious.)
Nostalgia isn't what it used to be.