Anyway - Kamen Rider is like the big brother of Super Sentai. It's a little more adult and takes on much larger story lines. Kamen Rider Kiva simply is the best - absolute BEST - of any Kamen Rider series. One of the key factors that kept me coming back to the series, episode after episode, was it's soap opera-like feel. It follows the life of Wataru and his father Otoya, both in separate concurrent time lines. Otoya, a womanizing violin master, is in 1982 -- and his son, Wataru, is in 2007. Wataru is Kiva, who uses his powers to fight vampire-like monsters called "Fangire". Wataru is actually very withdrawn from life, being a shut-in, but he gradually comes into his own over the course of the series. Many events from the 1982 period have direct effects on the the 2007 period. Both slowly begin to connect over the course of the series, as their the large cast of character begin to intertwine in genius and inspiring ways.
If you like Super Sentai - then I suggest you give Kamen Rider Kiva a try. It's a great series, much akin to Buffy the Vampire Slayer. Not just because of the goth theme, but because of the humor and action that is mixed together. It was simply a genius series which I was sad to see end.