I'm slowly working my way through this (just got up to 16, where Cobra joins a killer baseball league).
This show's got everything, loads of action, a lovable goofball but badass hero, tons of hot women, over-the-top villains, great music and animation that still looks really good today.
Illuminati, the group that scans Riki-Oh, translated the first volume of the manga but dropped it. A real shame, but the show seems to follow it well enough.
Can't wait to see the new Cobra.