I can still watch that show & laugh, laugh, laugh. I think it was the characters -- they were so vivid. The show had an innocent silliness, yet was sophisticated in a weird way.
That's why I enjoy the older shows myself, there was no political correctness, no lecturing or moralizing, just plain fun and with characters that people could relate to. I'm still trying to figure out which theme song I like better, that of Gilligan's Island or the Beverly Hillbillies. :)