Wacky Races is great... the spin-offs aren't so great. There's just something fun about watching that classic show. I guess one reason is 'cause I got the Wacky Races Dreamcast game!
The other Hanna show I like, and cannot figure out, is Magilla Gorilla. They replicate the same music & sound effects as used in Flintstones I guess is one reason Im attracted to it... but it's just an enjoyable show to watch, along with the others that are squeezed into the show (The Peter Potamus Show, and that one with the little bird that sounds a lot like the one from Tom & Jerry... can't figure its name out).
Quality slipped in the 70's.
The 80's had Pac-Man,though!
Oh, and let's not forget about 2 Stupid Dogs... a great show that's a definate classic.
Greatest? It's all a matter of opinion... but the 60's era was my favorite by far.