Actually Tiny Toon Adventures aired on Fox Kids first as well. And as people have already said, Teen Titans was developed for Cartoon Network and repeats aired on Kids' WB!.
There are actually many shows that first aired on Fox Kids before airing on Kids' WB!: Batman the Animated Series, Animaniacs, Tiny Toon Adventures, Looney Tunes shorts (as Merrie Melodies on Fox and That's Warner Bros.! and Bugs 'N' Daffy on Kids' WB!), and even many of the Pinky and the Brain segments from Animaniacs that made up some episodes of Pinky and the Brain.
In Kids' WB!'s early years, I think that it was more defined by Animaniacs than any other show that you mentioned. Of course, things changed when Pokemon premiered. Nevertheless, people always mention Superman the Animated Series, but for whatever reason, that show just never lived up to the hype of Batman the Animated Series. Don't get me wrong, it was popular, but it never reached that upper echelon. Even today, Superman still lags behind Batman in terms of mass appeal and merchandising.
Also, I've said this before, but when evaluating the quality of shows that aired on Fox Kids, you have to look at its entire broadcast history and not just look at its later years. The network was run by different people from 1990-1997 than from 1998-2002.
I think it's very hard to restrict your lists to only five shows. Fox Kids ran for 12 seasons and Kids' WB! ran for 13 seasons. For that reason, here's 10 examples of what I think defined each block (in no particular order).
Fox Kids:
- Mighty Morphin Power Rangers (and its subsequent renamed seasons)
- Batman the Animated Series / The Adventures of Batman and Robin
- X-Men
- Animaniacs
- Spider-Man the Animated Series
- Bobby's World
- Eek! The Cat / Eek! And the Terrible Thunderlizards / Eek! Stravaganza
- Goosebumps / Ultimate Goosebumps
- Beast Wars: Transformers
- Digimon: Digital Monsters
Kids' WB!:
- Pokemon (and its subsequent renamed seasons)
- Yu-Gi-Oh! (and its subsequent renamed seasons)
- Animaniacs
- The New Batman/Superman Adventures
- Batman Beyond
- Jackie Chan Adventures
- Scooby-Doo Where Are You! / What's New Scooby-Doo?
- Pinky and the Brain
- Histeria!
- Static Shock
You may be asking why I didn't list Tiny Toon Adventures for either block...and that's because almost all of its episodes premiered in syndication. Yes, it did move exclusively to Fox Kids in fall 1992, but it had already run its course by then and come 1993, Animaniacs overshadowed it on the block.