If I was to rate them:
Orchid: 10/10
Morningrise: 10/10
My Arms, Your Hearse: 8/10
Still Life: 10/10
Blackwater Park: 9/10
I like the first two albums a lot. Something about the way they sound is just... different than most stuff out there. Plus I like the one-word names and cover photographs. I mean, sure Blackwater Park has an awesome cover, but it just looks too "polished" I mean, the picture on Morningrise and Orchid just... they make me think of beauty. Blackwater Park is more of an "Oh cool!" kinda reaction.
They're all very good, so you don't need to worry about buying a bad one. Just make sure you give each one enough time to sink in.
Morningrise took me longer to get into than Orchid did, but it's probably a little bit better overall.