Okay, so they aren't all really platformers. This is a nebulous category with side-scrolling beat--em-up, shoot-em-up, jump-on-their-heads and climb, run, jump, duck, crouch your ass off to stay alive. Basically, and side-scroller that isn't a horizontal shooter (i.e. NOT Gradius and R-Type). So, here they are, the best games from this genre that have previously been Games of the Day...
1. Biomechanical Toy
2. Black Tiger
Medieval Conan-ish side-scrolling fun
Great graphics and rich colors make for a fun ninja-esque romp.
From 1999, a newer Ninja beat-'em & jump-it.
5. Charlie Ninja
Rich, cartoony, Old-West graphics with lots of humor and imagination.
6. Chelnov: Atomic Runner
Run & jump your way out of a bad situation. Simple and compelling.
7. Armored Warriors
Exceptionally cool Mech beat-'em-up with tons of add-on weapons.
8. Thunder Hoop
You are a goofy slacker trying to make your way through a factory of doom.
9. Magic Sword
Traditional sword fighting side-scroller - highly polished in all aspects.