Cadbury is nice and everyone loves it, but I've come to prefer Whittaker's to Cadbury recently. It's a New Zealand brand available there and in Australia, and I don't know elsewhere. Cadbury is just too sweet sometimes and Whittaker's just seems to have more depth. More "meaty", if it's not too absurd to apply that term to chocolate. I find Lindt a touch overrated, I always get sick of it after a few pieces due to its richness. And yeah, every Hershey's I've tasted has been crap. I've only had Godiva once I think and it was heavenly, though expensive.
Best white chocolate - Nestle Milky Bar. It's addictive stuff.