Time Odyssey for me is way up there. I love that album. His playing and writing is mind boggling. While My Guitar Gently Weeps is ridiculously good!
And I'm with JDub on Howe's first album. Buying it now and hearing it probably makes your ear hurt because of its Shrapnel cliche-ness; however, when that album came out, it was earth shaking. Howe's playing was out of this world. The four-note-per-string tapping he did was psycho for the time. And his phrasing was absolutely phenomenal. In the context of the time that album came out, it was beautiful. No other word for it.
If I was to compose a list, it would be made up of time-contextual albums rather than what I think is great right here and right now. I'll see if I can put it together in order of impact for the time it came out. I don't know that instrumental music has quite the profound effect on me that it did in the '80's, and my favorites still come from that era. The music from this time, though many label it "cheesy", set the stage for a grand evolution in musicianship and virtuosity for all guitar players who have followed in the insert-whatever-metal genre since.
1. Yngwie Malmsteen - Rising Force. You can't say anything bad about this CD from a time-contextual perspective. Most members of this forum were not even born yet when this CD came out. I had just started playing guitar at this time and my mindset was typical Iron Maiden, Saxon, Ozzy, yahda yahda (insert early '80's metal here). But, when I picked up my first issue of Guitar Player magazine in 1984 and read about this kid, I had to check it out. When I finally got the cassette, my world changed. And that's what happened to myriad other guitar players in the '80's. Just ask Paul Gilbert!
2. Tony MacAlpine - Maximum Security. Another one that set my ear on its edge, though the effects to the guitar community were not as profound as Malmsteen's.
3. Vinnie Moore - Time Odyssey. A sophomore effort that completely went against Shrapnel's cliches. Good grief, this music was astounding, and the picking is unreal in its articulation. How can anybody play so fast with such attention to every note?
4. Steve Vai - Passion & Warfare. No neo-classical shred, just crazy-ass guitar playing over crazy riffs and mind-boggling atmospheres. I saw Steve Vai on the Skyscraper tour with David Lee Roth and didn't touch my guitar for a full week after that. This from a guy who put in 6-9 hours a day as a kid. I think that's a rather profound statement in and of itself.
5. Greg Howe - Greg Howe. Back in the day, I think he was obscured by MacAlpine. My first listen to the soundpage in Guitar Player immediately brought MacAlpine to mind, and I figured he was merely a clone. Then I got the cassette. Boy, was I wrong. Then Howe II came out and I was floored. Bad Racket was phenomenal, and, as I stated before, Howe's phrasing was ear-boggling at the time. Then I was fortunate enought to see Howe II live and meet the band. Just incredible. Speechless even.
That's about what I have.