Yngwie Malmsteen and Cacophony are kinda like...virtuose guitarist, or how you call them. Its like trying to play something from Paul Gilbert or some other crazy ass dudes. I would say Megadeth, the beginning of their songs are often quite easy, but its getting harder and harder, especially their solos. Mustaine is a king in old skool pentatonic shredding and Marty Friedman has also some very difficult solos.
And i also have some respect for alexi. Like RjBeals said here.
must...play...more...guitar...must!!!