I like Ryuki. After all, this and Kiva are things, that made me a Kamen Rider fun. Also, I heard, that Ryuki was a real blast in Toku fandom, when it was airing.
I agree that Yui is awfull, fights are not that good (just.. where have you seen good fights in KR? Well, in Tokusatsu? Just a few titles like Garo, I guess) and some of actors are just awfull (but just look at main cast: Satoshi Matsuda, Kenzaburo Kikuchi, Tomohisa Yuge, Takashi Hagino, Kanji Tsuda, Hitomi Kurihara even Ryohei and lots of others. Can someone accuse them of poor acting? Suga certainly isn't the best actor ever, but he was decent enough for me) Some guest actors were just bad, but it's not that bad overall. Plot was poor, but it was a bit experiment in KR, so it was more or less enjoyable for me. Ryuki brough a lot of good things to the franchise, it's pointless to deny that.
It's a good Tokusatsu series for me. Not the best, yet good. I prefer to watch Ryuki, than shows like Den-O, Decade, OOO or Fourze.