A few random thoughts on the topic
1) Godiva USA qualifies as a "crime against humanity". How they could take a good product and turn it into absolute crap is a mistery of marketing. It's even more expensive than genuine Godiva...
2) US chocolate sucks, as a rule. There are exceptions, though: Berkeley's Scharffenberger (if you are ever in Berkeley try and visit "Cafe Cacao", their factory restaurant). Starbucks Dark is not bad either.
3) BRU duty free is the place.
4) Italian Gianduiotti, hazelnut (?) chocolate. Very yummy.