Honestly, I'd say 1998-2003. More classics, and even the worst originals seemed to be offset by more classics.
I first got it in May 2002. You had classics, then that summer they did morning and evening marathons of a few 70s and 80s classics. I loved coming home from work to catch the originals (mainly Russian Roulette and Whammy). Rediscovering the Marshall Hollywood Squares was icing on the cake, not to mention the Feast of Favorites that Thanksgiving.
However, 2001 was pretty good as well. It was right after they experimented with that awful DJ Games, but they made up for it by putting CBS TJW, and a few childhood favorites such as Super Password and Eubanks Card Sharks.
They did squeeze the credits at that point, but it was only for about 20 seconds, so you still heard a fair portion of the closing theme.