All these Kiva haters. Its not really SURPRISING (Double's the first thing I've seen received so well while new), but it is somewhat disheartening. I enjoyed Kiva. Not like I enjoyed Kuuga, Blade, or Agito. Not even like I'm enjoying W. But I enjoyed it quite a bit.
I will admit I am a bit biased towards Kiva because it was my first dive into Japanese Toku, but I enjoyed it a whole bunch. I enjoyed the characters, the designs, and particularly the music.
I voted for Ryuki. but it was a really hard pick. I haven't seen Kuuga or Agito

() So I crossed that off. I also crossed Kiva off because I actually loved Kiva, despite the huge ass flaws, I could never see it as the worst.
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Ryuki - I actually really like Ryuki's design and initial concept. However, with a Rider total like that, a majority of them where characters you never got to know. They were introduced and killed. Shinji was pretty much a dumbass, but likable. The ending kind of threw me for a loop and left me going "what the hell was the point again?" That never really settled well with me, which is probably where a majority of my distaste for the show comes from.
Faiz - It started off really good, and actually kept going fairly well, but again, a lack luster finish. A handful of the characters were pretty much just irritating, and it tried to be a bit too grimdark for it's own good. It just kinda trailed off and ended. I still really like Faiz, it just wasn't all it's cracked up to be.
Blade - Great concept, excellent twist, but lord Blade didn't know what it was trying to be half the time. Like Lynxara said, it had a little bit of everything in both character, plot, and storyline. Again, I enjoyed it, but I wish it had a bit more of a one track pace.
Hibiki - Speaking of one track paces...Lord I loved Hibiki. Yes, I know it lacks action, the staff changed, and the show kinda took a small turn for the worse, but the character driven focus on this show caused me to love it. I'm a very character and story driven viewer, so this was definitely one of the shows for me. My only big complaint is that I wish it had a bit more of a plot.
Kabuto - I really loved everything about Kabuto, all things considered. Most of the flaws people already pointed out, but I liked the diversity the show brought in characters, and by this point, I was used to shitty endings for Rider shows, so Kabuto's lackluster "wait, who is that?" finale left me fairly satisfied.
Den-O - I went into it expecting to hate it, but I came out loving it. It could be better, it could be less of a money making whore, and sure it probably killed my beloved Kiva's chance of being popular, but it still made me laugh, and the concept itself is fairly nice, even though the show itself is fairly weak.
Decade - For what it is, I really liked Decade. I liked seeing the AU worlds, I liked the cards, and I like the kind of merchandise it brought to the fray, but I have to agree with all the complaints. Decade had no story, and when it did, it didn't know what it was doing with it, and it ended up leaving it behind in whatever world they were in.
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It was a hard pick for Ryuki, Decade, Blade, but Ryuki ended up winning due to that ill taste it left in my mouth after the finale.