Define best. I think there are all sorts of opinions on best, although I think it would involve something really rich that you don't want to consume in mass quantities. I'm thinking maybe best experience, and for me that's Fenton's Creamery in Oakland, California. It's not super rich or super expensive, but I have fond memories of the place, even when the ice cream itself might not have been as good as it is now. I think it was mostly the cheap prices that I remember.