Definitely Dragon Knight. It's a show that has a darker and more complex storyline than what you normally see in Power Rangers, and that includes RPM. The show goes through stuff such as trust, betrayal, loyality, trechery, etc. While the storyline for it is "good vs. evil", sometimes you might see evil Riders fighting other evil Riders, like the one that's coming next week. And you've got General Xaviax, who is one sinister and cunning villain. No villain in Power Rangers has been as threatening as Xaviax is, and there's no "Monster of the Week" in the show. Plus Len/Kamen Rider Wing Knight is the fighter in the show because he's played by 5-time martial arts world champion Matt Mullins. Do you see anybody like that in RPM? HELL NO! And most of the characters in the show are like anti-heroes, and that's what I love.
Now in terms of how faithful it is to the Kamen Rider franchise in Japan, its storyline is not directly copied off Ryuki, but it does feel like a Kamen Rider series regardless. It's like a mix between the Showa era (Black and Black RX) and the Heisei era, with a little Ryuki mix into it. For example, what they got from the Showa era, you've got General Xaviax, a central villain, original motorcycle props for Kit and Len, spinning advent decks on their belts (like the Typhoon Belt from the original 1971 Kamen Rider), and the occasional teamup between Kit and Len, kinda like what Ichigo and Nigo did in the original. What they got from Heisei was Riders fighting other Riders, a dark, dramatic storyline with mystery, developments, and all that ****, and each episode ends by building up to the next episode.
I'll admit that I don't like any of Maya's friends, but that's just a minor flaw for the show.
As for RPM, it had an awesome premiere, but I felt it went downhill because I thought this was gonna be different from the previous Disney seasons, but nope. It's starting to regain the goofiness that it usually has. And I was hoping that this would be MUCH better than Go-onger because of the premiere, but because o the kiddy comedy and silliness from episodes 3, 4, and 5, I hate to say this, but it's starting to be LIKE Go-onger, and I don't like Go-onger at all. Maybe it'll get better when Judd Lynn takes over as the head writer again. After all, he did Power Rangers Time Force, the best season of all time.