It doesn't have my favorite Don or my favorite Leoporello, but for all around excellence you really can't beat http://www.amazon.com/Mozart-Don-Giovanni-W/dp/B002N4DZ2G/ref=sr_1_17?ie=UTF8&qid=1328624507&sr=8-17

This recording is the gold standard. Like I said, there are other singers who sing some of these roles better (for me, no one beats Thomas Allen as the title character and I'm quite fond of Terfel's Leoporello) but as a whole I do think this is the best recording of Giovanni there is. Sutherland is great and Schwarzkopf is without question the greatest Elvira I've ever heard. Not to mention Alva's Ottavio, which is about as well sung as you'll get.