Compare that to a bland slog like Kamen Rider OOO ... who in that show is really memorable? Aside from Eiji and Ankh I have a hard time remembering anyone beyond their one note gimmick ("I BAKE CAKES LOL").
Is it really productive to build up a series by vaguely stepping on another one?
If the only thing you remember about Kougami is that he bakes cakes...then you didn't pay ANY attention. And that's on YOU. Maybe Kaixa was memorable, but what about the snively Clover member? Or the female Clover member? Or the kids from the academy? Or the one-note Smart-Brain poster-chick? Were they more than their one "gimmick"?
OOO had characters, just like 555. Which ones you personally connect with is no measure of their quality. Characters like Kougami, Maki, Date, and Gotou bear tremendous thematic weight in OOO, which is heavily driven by its themes. Faiz is not driven by its themes; it's driven by drama. The characters will not be described or utilized in anything like the same way and it's wrong to expect them to be.
As for the ending. People argue that it doesn't have one ... and? Not every story needs to end in a neat, tidy Toku bow. In fact most Kamen Rider endings are pretty bad to begin with. I'd say Kamen Rider 555 is more about the journey and in a way the ending fits in well with the tone of the series. It doesn't really "end" because nothing ever does.
Wrong. Stories do. STORIES end. Otherwise they're not stories. If you aren't going to complete any character's arc, show something about the human (or ophnoch) condition, or relay a memorable series of plot points from beginning to *end* then what are you doing? What's the point of watching?
"A man took a walk around the block, he met a guy and a girl and another guy, and a few more guys, he didn't like that one guy much but that other guy likes the girl, there were some guys that didn't want him to get the store but he stomped their asses and put one in the hospital. Two of the people he met along the way fell off a cliff and then he..."
See, that story there is just like KR 555. It sets up (very vaguely) a lot of relationships and conflicts, goes in circles for a bit, kills off characters not to conclude their arcs but as a prop to continue other characters' arcs...and then doesn't finish. It's not a complete story.