BWP, Watershed, MAYH are my faves, in that order. BWP is like the culmination of the old style Opeth with the new style, and I really dig the production as well, the best up until then (8 tracks on each side for rhythm guitars? fuck yeah). Watershed is probably the best so far, from a production standpoint, the songs are also great. MAYH is just a good ass album in general. With that said, their older albums, Orchid, etc., are good as well. Like someone said, Opeth has changed with every album they have done. I suggest going on YouTube or something and trying to find songs from each album to check out to see which one(s) you think you would enjoy as a whole.