Blessed are the Sick is my favorite M.A. album. Nothing else that I have heard can quite compare. Though I haven't heard Altars of Madness in its entirety yet (yeah, I know, shame on me).
Covenant and Domination are more commercial, people tend to lambast Domination in particular, but it's still pretty cool, though Covenant is the better of the pair.
Formulas Fatal to the Flesh and Gateways of Annihilation feature a different singer, not David Vincent. They aren't up to the band's best moments, but Formulas in particular is quite underrated and boasts some damn cool death metal - I really enjoyed what the band was doing on this album in terms of the sick-ass timing changes - it's like the moment on the rollercoaster when you have risen to the highest point, and you start the rapid descent and it feels like every organ and innard is churning, convulsing, peristaltic ecstacy.
Gateways has a few slower and mid-paced songs, frankly, it's not all that exciting although there are a few cool numbers and the drumming sounds a little too precise in places. I mean, the drumming is still great, I could care less whether triggers were used to achieve the sound...but there is something within the actual drum sound that is just...artificial. Not a bad album, but not really up to par with M.A.'s other material, IMO.