5th gen was definitely lacking in 2D platformers.
The most famous one, SOTN, is not really a pure platformer and is more aligned with RPGs. You can not die from falling to pits in SOTN.
There's of course a bunch of games like Goemon's Great Adventure, Klonoa, Tomba, Astal, Clockwork Knight and also some more obscure ones like Fuun Gokuu Ninden. But with the exception of some of those, like Goemon which is really excellent, the rest aren't comparable to the best stuff 3rd and 4th gen had to offer in the genre.
Yes, it's infuriating because, just as the technology was most optimal for amazing 2D, the money was on 3D, making 2D games be more budget projects.