The first 5 I've really decided on are the first releases from:
Death - Scream Bloody Gore
Deicide - Serpents of the Light
Morbid Angel - Abominations of Desolation
SYL - Heavy as a Really Heavy Thing
Meshuggah - Contradictions Collapse
Any suggestions are welcome, and yes I did a thread search but there seems to be no real definitive list of classics of the genres.
City instead. It's a much better album.