I think this is pretty easy. As much as I love the CCBS System, Bionicle offers just as much, if not more. It had a piece for just about everything, a more riveting story, more well defined characters, and an overall greater atmosphere.
Hero Factory is OK. That's pretty generalized, but it's true. The Sets were kind of split for me. You either had some interesting CCBS Builds and a Parts Pack that gets you some pretty nice pieces or you just got a hunk of Junk. Evo Walker, I'm looking at you. I love the system; it allows for quick and easy armor, with some detailed clippings to boot, but that can't be the saving factor of a theme.
Slizers (or Throwbots for us 'Mericans) was pretty Meh. At the time of its release, we could've said it was one of LEGO's Most Daring projects, but now? Not so much. Most of the builds were pretty basic (Besides some of the Titans) and had some pretty character specific pieces. Have you ever seen somebody use Amazon's Face piece in a MOC? I'm pretty sure you haven't (But if you have, please give me a link...)
While I'm at it; I'm gonna bring up some Bioni-cousins. Robo-Riders are on the same train as Throwbots, but a bit more lame. The DC Superheroes are pretty good parts packs, as well as their Marvel Counterparts. I've never really touched the Chima and Star Wars Ultrabuilds, so I have no comment there. Finally, Ben 10 was cool as a concept, but was not executed very well.