Though I haven't finished watching the show yet, I really enjoy Kamen Rider Ryuki. Though I didn't at first, I know quite enjoy the Rider war aspect of it, and the Mirror Monsters is a great concept.
Additionally, the SH Figuarts line for Kamen Rider Ryuki is fantastic. Of all the many Figuarts I have, the Ryuki line is the best one, for posing, for quality, for sheer number of accessories. As such, I am most definitely a completist when it comes to the Ryuki line of Figuarts. I highly recommend any Ryuki Figuart to anybody.