I can only confirm what you said. BG&E is a pearl of quality between dozens of games (but they sold better.. it's a shame). It's truly the atmosphere what makes this game unique, also there are many details and a good story, well I can only repeat what's already said. If you liked Zelda play this game, it's worth!
Btw: Ubisoft is yet unsure whether to make a sequel of BG&E or not. In germany we're collecting subscriptions to change their mind into the right direction. Personally I guess it was the bad marketing why it sold so bad but maybe people just don't want good games anymore (but brainless shooters like UT instead).