Forgot to mention that every Morbid Angel album has something great to offer. Even their weaker material has at least 3 flat out incredible songs. I prefer the Vincent period to Tucker, but that dude is nearly as awesome (except Formulas, the only one where the vocals just aren't up to snuff).
Invocation of the Continual One is one of the most epic songs ever, and easily the most epic death metal song I've heard. It also contains my favorite guitar solo ever, or at least top 5 material.
Trey Azagthoth is probably my favorite guitarist ever, metal or otherwise. The dude's playing is frickin' inhuman. Like Papa said, NOBODY plays like that motherfucker. Just listen to any of their riffs, even the imitators can't pull it off. His solos are another thing, not even worthy for discussion. Particularly Where The Slime Live solos... *raging guitar shaped boner explodes with delight*