Exaclty. The Fliesher cartoons are so impressive in animation just because of the era they were made in. When most cartoons were super-simplified anthro-animals, these cartoons had human beings that moved like real people. The stories were nothing to write home about, but the animation is good enough that it doesn't matter.

The Bruce Timm cartoons are from a different era. The animation is not bad, but it was a step down from B:TAS, which set the standard so ridiculously high. Superman's design was pretty good, but the lack of a Gold Emblem on the cape and the dots for eyes hurt it. Still, it looks enough like the Fliescher cartoons that you could concievably see them as hapening in the same general section of the Multiverse.

Technically, I think of the Fliescher cartoons Superman as Kal-L, the Filmation/Superfriends cartoons as Kal-El, and the Superman of S:TAS as Post-Crisis animated Superman. (After all, Superfriends ended in 1985, same year Crisis happened)