Ren and Stimpy was great on many levels: the story telling, the model designs, the animation, everything about it was perfect. I wouldn't say Doug is up there in terms of animation-wise. The designs for it are the ugliest things on the planet, but the writing was pretty decent from what I remember.
There are some animated shows that have come and gone over the years. Some of which were heavily impacted by the works of Spumco as well. Sponge Bob being the prime example.