Blade, without a doubt.

Faiz (I'm slowly working my way through it now), Balde and Kabuto. Mainly cause they're the only ones I've seen anything out of.

Kuuga (the multiple-form thing will sell toys like mad)
Faiz (because those finishers are the epitome of awesome)
Kabuto (perfectly merchandisable and Clock-Up-able)

Though Agito and Hibiki, and Blade should also be considered. Every series should.

555, Kabuto, Blade and I could see Hibiki, But I wonder how they would do with the recurring riders.

Personally, I'd like to see them work their way forward. I guess it depends on what they've got in store though. I'm curious if a Hibiki adaptation could even be pulled off though. After seeing a few episodes, they appear to have a very unique style of filming. I'm probably getting too far ahead of myself though.

That film student stuff in Hibiki stops after the first five episodes(thank GOD). The suits and monsters could work, but they'd have to film a lot of their own action shots. Hibiki would be a perfect series for filming in New Zealand though since a lot of the fighting took place in forests.

Eh, I don't know about Hibiki. If the US version of Hibiki airs in American TV, people probably will say, "THAT IS NOT KAMEN RIDER!!!" It's up to Steve Wang for this.

Ryuki isn't based on insects, Form what your saying as "Not Kamen Rider". Remember KR america starts with Ryuki/DK, So Fans will have a diffrent veiw on the legacy, if the show picks up.

If Hibiki dose get adapted, It would be cool if they have more footage of the less show riders(ie Danki, Eiki)

Thinking through it all, Blade makes the most sense, since the card theme is extremely prevalent there, which would tie it to Ryuki wonderfully. Plus the fact that I love Chalice doesn't hurt.

And the merchandisers will love it. Collector cards with each toy, a card game...