There were a ton of excellent Nickelodeon cartoons in the 90s and early 2000s.
But, based on absolutely nothing, I would say "Hey Arnold!" was the most popular of the bunch. It had great characters, a great setting and a lot of heart.
The results are pretty excellent. They're so good, in fact, I think Nickelodeon or Netflix or someone should commission a new series based on these renderings.
I would binge-watch the crap out of that.