Centurions! Ummm, *racking brains*... Lead characters Jake Rockwell, Ace McCloud and Max Ray, bad guys Doc Terror and Hacker... supporting cast Crystal and some ape thing (I don't know why, the name Lucy's stuck in my mind). And yes, that's from memory (sad ain't it?), that show kicked arse (and wouldn't it be good as a live action flick?).
Transformers has to rank right up with the best of 'em (Optimus Prime, Best Hero Ever...), a little remembered show called Starcom had the best toy line up that's ever been made, but the best show for me wasn't a cartoon, was a Japanese puppet show called "Star Fleet" - great sci-fi, plot that actually went over the length of the series and some real memorable ship designs.