So far, I would say Kabuto. Great suit designs, awesome characters such as Kagami, Daisuke, Tsurugi, Misaki, Tadakoro, & Renge. The only problem I had was that Tendou was acting like an ass thoughout almost the entire show, plus the ending was the biggest failure, not to mention that there wasn't an overall plotline.
Den-O on the other hand was a bit too light for me, because of the over usage of the comical lines, and no serious points to the story itself. At least the characters, the imajins, and the weapons had some originality in the designs, especially the Den-O Belt.