Regarding Shadowmoon: In KR Black series, he is not a Kamen Rider, because only Black called himself as a "Kamen Rider" since both of them are "Century Kings" and Black wasn't brainwashed unlike Shadow Moon. Hence Black calling himself a "Kamen Rider" for the purpose of rebelling against Gorgom, and Shadow Moon a Century King by default.
Regarding Tackle: No official word whether she's really a Kamen Rider since it has always been a rule when Sensei Ishinomori was alive that he gets to declare who is and who isn't. Sadly, he died before completing the draft of Tackle's character, hence her being vague. But she is considered to be a Kamen Rider because she followed the guidelines of a female Kamen Rider character as per Sensei Ishinomori, a. Must have Henshin Sequence, b. Must have Rider Kick, and c. Must die. I'm not totally sure if Toei followed the rules eversince, but if you noticed, most female Riders before gets wasted.
Regarding Riot Troopers: The only real Kamen Rider in KR 555 series in general are Faiz, Kaixa, Delta, Psyga, and Orga, but in concept, the Riot Troopers are also Kamen Riders because it follows the requirements of being one in the series, which is to must be an Orphenoch or atleast have the Orphenoch DNA. The Riot Troopers are not considered a Kamen Rider by many because it is weak and tends to be fodder, but since it was mass-produced, it tends to be weaker, hence not having the signature KR stuff the likes of Faiz has. Just consider the Sherman tank, it's considerably weaker and had none of the technological advancements that the Tiger Tank has, but it's still a tank.
Regarding Another Agito: The term "Kamen Rider" almost never existed in the KR Agito series since the guys who had extra-ordinary powers and can henshin were called "Agito". Gills was a failed Agito and Another Agito is literally another Agito. I don't even recall G3 being called Kamen Rider G3, if he ever was, I guess because of the fact that it is some guy wearing a suit, hence being "masked".
So given these explanations, you would notice that the term "Kamen Rider" is simply a franchise name used by the recent toku shows, and only a few has dared used the term "Kamen Rider" within the series because let's face it, the writers come up with a story not because they need Kamen Riders to have a story, it's because the Kamen Rider franchise needs a story every year like in the case of most Heisei Rider series (heck, some of the Heisei Rider series was supposed to be for Metal Heroes or something entirely different, but the franchise managed to acquire them instead), but Decade was able to change all of that by becoming a medium of all different stories in the Heisei history to give them a common denominator, hence showing that they are just part of the franchise if you look outside the box. Double on the other-hand masterfully used the term "Kamen Rider", having the explanation of being a masked vigilante, hence having the power to use it (this was all explained during the episode with a girl being told that her dad is Double since her dad was supposedly scarred and had to wear a mask, he was also called "Kamen Rider" by witnesses and even on the radio) (IIRC, some series used this technique also to be able to use the term within the series)
So there is really no use debating the usage of the term "Kamen Rider", because let's face it, only Shotaro Ishinomori had the right to proclaim who is one, and Toei had to continue his legacy and are using different ideas which causes confusion to some.
Regarding Diend: Contrary to everything I just said, that bastard doesn't deserve the name "THE-END", let alone be called a Kamen Rider, he's a disgrace! All he does is Henshin, steal, summon, get creamed, and INVISIBLE! And occasionally a Final Attack Ride, but. The bottom-line is, he's a cowardly @sshole who is just so damn irritating because he appears out of nowhere for God knows how, runs his mouth, and cowers away! F*ckin useless character IMHO!
EDIT: Corrected some information regarding Shadow Moon.
