The thing that sets Satch, Vai, Malmsteen, Petrucci, & Gilbert apart from Loomis is MEMORABLE SONGWRITING, HOOKS, & MELODIES.
Jeff has proved it with his solo album. While it is full of cool shred guitar and "pyrotechnics" it lacks emotion and feeling in some places.
If you listen to an album by any of the aforementioned (for Gilbert the Mr. Big stuff) you can hear mature honest songwriting and amazing sense of melody.
While Loomis has command over the instrument the guys above dont command the instrument, its just an extention of their body, imagination and minds. Its a tool to express their emotions.
Finally to anyone who is like SATCH WTF???? Hes the only instrumental rock guitarist to ever win a grammy for a solo album. Not even Vai has topped that yet. In addition keep in mind if it wasnt for Joe, there would be no Vai.
Joe has the most emorable melodies of any of the guitarists mentioned above. While hes not a big "pyrotechnics" guy, he still can do it all. Try playing the arpeggios from "The Enigmatic" from not of this earth. I got $50 says they are the most difficult and odd thigns you have ever played, I would dare say even Loomis couldnt.