Well, in my Rider shows I usually like having a coherent overall story, very genuine heroes, good designs on both the Rider and the monsters, and well done action (be it realistic approach to the style of fighting or wild to-hell-with-physics style). I tend to be turned off when the storyline or the powersets have gimmicks that I feel are silly in a way that is incongrous to the idea of superhero action series or at the very least Kamen Rider itself.
So I tend to not like cardbased series or musical insturments etc. This is also why I find the cookery antics in Kabuto very distracting even when I'm really enjoying the main plot and the action. It's important for me that more often than not Kamen Rider be heroic, so the Rider vs. Rider trend while it can be intresting at times is a little offputting in how standard it's become. I kinda hate seeing total assheads like Ouja and Kaixa bearing the name Kamen Rider. I think it would be better if villan Riders simply had their own designation the way Shadowmoon did. But, oh well.
Most Favorite KR:
Kamen Rider Kuuga: I just really liked and admired the character of Godai Yuuske. (I prfer him to Shouichi to). He's someone who thinks beyond himself and strives to help people find their smile again even in dark or difficult times.I enjoyed the overall plotline of the show and it's realworld feel. I thought the Grongi were one of the better kaijin concepts and in the show they feel like a genuine threat. It's creepy as hell to imagine being on the street and encountering them. Good character interaction, great music, and plenty of genuine emotion. Kuugas red Mighty Form is prolly my favorite design because it's bold yet simple and conveys a real sense of heroic power.
Kamen Rider Black: I liked Minami Kotaro for his feirceness and sense of justice counterbalanced by his easygoing, fun loving side. Since this is an older series it's more episodic but most of the episodes still work really well and there is the ever present plotline building to Shadowmoon. The Golgom are devious and creepy. Great suit and kaijin designs, awesome action in the classic style yet also kinda modern to. I love little things like Kotaro telling the Golgom he won't forgive them or the announcer saying "Tatakae Minami Kotaro!" This is another series where I really liked the music. Long Long Ago 20th Century remains my favorite ending theme of any series in any genre. (I consider the new "end" themes to be fight songs and I have a fave of those to.)
Other Rider works that I thought were ok: Original Series, Agito (The Uknown are excellent kaijin designs!),V3, ZO. I actually want to see more of the original series but I've seen enough that I can already tell that I like it. It's always really intresting seeing a longrunning hero in his most primordial form. I'm kinda weird though in that I actually like Rider 2's Old One design better than his later one.
Least Favorite KR: Blade, Hibiki, SkyRider, Amazon, RX, Shin, J. The First (It came so close to rockin. So damn close and then Cobra/Snake angst destroyed it.)
KR that leaves me saying WTF?: Ryuki. I actually think the Mirror Monsters are a cool Kaijin idea (great designs) and there's a certain neat mystique to it. I can even see some merit in the premise. You could think of it as the Rider fight is the evil originzation (metaphorically) and Shinji gets this power somewhat against his will but then turns it on them. But to me, the show never seems to maximize that potentinal. It seems to just sort of delight in Shinji failing and the other "Riders" being selfish. I hate the CCG card slashing but I kind of liked the slamming the deck into the belt henshin. It made me wish the deck was the "card" that held magic or data for their powers. The four endings thing I think is really silly and the story and characters are ...well, it could have been alot better. JMHO of course. I will say though that Ryuki does have some good action and suit acting. A good example of that whole second school of thought on it that Mark Musashi talked about in that interview.
I'm still watching Faiz and of course Kabuto. Faiz is my favorite mechanical Rider design and there's alot I enjoy about it, but man..I'm starting to think I liked the show it was when it starts better than the show it becomes. Some good action later on though when they make the fights a bit longer and have them it other parts of the episode besides the tail end.
Sorry for the long post.