The best Apple OS? NextStep. It did almost everything OS X does, and ran well-on 30mhz Motorola 68030 chips. Did I mention it did this almost twenty years ago? True geeks will remember it's final days as OpenStep, when it ran on PC hardware as well as Next, When it was the easiest cross platform developemnet system ever. Those were the days.
The best Apple OS of al time? The one they bought and killed.
The Great Tiger Giveaway