Having recently replayed Baldur's Gate 2, I can testify that it is, in my opinion, BioWare's most intricately crafted and best-paced game. In comparison, most of the other, newer ones (with the exception of DAO, because of its looooong development cycle) feel a bit rushed.
The locations, in particular, are designed with utmost care and given immense flavour, internal diversity and entire lives and ecosystems of their own (I still consider the Irenicus's Dungeon opening as the best tutorial-level ever, the best narrative introduction, and the best-designed level in gaming). I must admit, I felt more for the touching character moments in the Mass Effect trilogy (especially Tuchanka in ME3), but ME never had levels this interesting - in fact they are too often dreary chest-high-wall arenas with pretty skyboxes. I preferred ME1 locations like Noveria and Feros.