I've had five, admittedly I'm only 24, so probably not as many as some of the old timers on here.
As for the best?
Hands down, that would be my current, a two-year-old Rottweiler. I've had him since he was six months old, barely more than a pup. Since he was the first dog I had as a pet after graduating college and getting my own apartment I had plenty of "alone time" with him to teach him how to do things right. He so well trained he knows how to signal me when he wants to fool around, we have our fun time on a futon, and he'll go put his paws up on it and look at me expectantly (Lol! Get over here and assume the position, I need to dump a load in your ass.) But unlike some dogs I've been with, he's learned to not just "shoot and scoot" he'll actually patiently stay mounted and leave it in while I get my rocks off as well. Then when I'm done, he'll slide out, wag his tail and then go smoke a cigarette (or whatever the dog equivalent is after sex).