Extreme isn't purely a wankfest instrumental solo act so it automatically tops basically everything else. Eric Johnson is probably the best guitarist mentioned in this thread but he's not really a shredder (though Cliffs of Dover is essential). Satriani and Vai have some pretty good songs. Yngwie and MAB are essentially legends at hitting the most notes per second but have pretty much no interesting content whatsoever. John Petrucci's solo stuff is a little boring but there's some really cool riffs in the midst of all of it, and Dream Theater obviously has some occasional good stuff.