alriiiight, time to post in my own thread!
Obviously this is just drawn from what I've heard.
2008, so far- DSO: the Manifestations collections and Opeth: Watershed are strong contenders, with Arckanum, Nachtmystium, and Enslaved close behind. Need some time to listen to all of 'em more.
2007- My solemn vow of DT fanboyhood obligates me to say Systematic Chaos. If not for that, Fear Of A Blank Planet/Nil Recurring, Phantom Limb, Fas, or Two Hunters might have a shot
2006- Skinless: TTWHTD, closely followed by Oath Bound, Blood In Our Wells, Identisick, Watching From A Distance and Instinct: Decay... 2006 and 2007 both ruled.
2005- Octavarium...? Nah, Crush The Insects! Or Annihilation of The Wicked. Hmmm.
2004- SMRC , of course.
2003- Train of Thought.
2002- Porcupine Tree: In Absentia. (Six Degrees was meh.)
2001- Opeth: Blackwater Park