Ok time for me to step in. First of all I am shocked not to see Mr. Val Allen Wood on these lists! lol...here are my personal favs when it comes to shred guitar. Note: When I say "shred" I don't mean people vibrating their picks over the strings as fast as the can and playing chords underneath. I mean the use of lead guitar to convey feelings in the way vocals usually do. Obviously speed techniques and such are effective in this. To better understand, look up the people I list below on Youtube. These are in order of my most to least favorite.
1. John Petrucci (Dream Theater) Very successful in his career with DT, but also his solo album Suspended Animation is one of my favorite instrumental albums. Look up a supergroup called Liquid Tension Experiment as well, as he played guitar in that.
2. Steve Morse (Deep Purple) Deep Purple is the most well-known act he's been in but he has plenty of other bands as well. One that you all might enjoy would be the new supergroup with Mike Portnoy (former Dream Theater) and Neil Morse as well as others called Flying Colors.
3. Joe Satriani (Chickenfoot) Don't get me wrong, I really don't like the band Chickenfoot lol. Its Satch's solo albums that blow my mind every time. Some really incredible guitar work, especially on Surfing with the Alien, The Extremist, and Super Colossal to name a few.
4. Paul Gilbert (Mr. Big) This is a guy for those of you who just want crazy fast solos and stuff like that. He does know his theory and plays some pretty melodic stuff as well, but he's known for stunts like playing with Drills and teeth. Guitarists, look up the lessons he's written for Premier Guitar magazine.
5. Michael Romeo (Symphony X) In the neo-classical style of Yngwie Malmsteen, this guy can play fast. But on top of that, he plays some pretty emotional stuff on both lead guitar and acoustic stuff. Listen to Symophony X's "The Odyssey" to get a picture of what I'm talking about.
6. Michael Angelo Batio-This guy mostly does solo project stuff, which is all mind-blowingly metal. I believe he was voted the world's fastest guitarist by Guitar World magazine as well. Not a ton of feeling in his playing but its alright.
7. Yngwie Malmsteen (Rising Force) We all know this guy. Crazy-haired Swede with jewlery hanging off his wrists and neck and chops to cut through an elephant. I can't really get into his music because it all sounds the same, but his speed and neo-classical licks are definitely something to be admired.
Anyway, that's my list. A lot of the people you guys mentioned are pretty legit as well (Carl Grimmark!!!!!). Oh, I also can't leave this conversation without mentioning that I think Syn Gates is annoying as heck. Other than Afterlife, So Far Away, and Nighmare, all of his solos sound like random noise to me. He's got some cool technique but that's it lol.