As far as continuity goes...
-There was the original Showa Continuity, that ran from the original Kamen Rider up to Black RX, in spite of some attempts to break away from it (Skyrider was called just "Kamen Rider" and broke away from everything before it... only to tank and bring back the previous Riders to rescue the series. Black was supposed to be standalone, but Black RX brought back the previous Riders again).
-The 90s movies were standalone, but there was a small crossover special featuring the new Riders and villains of their own movies and the previous series.
-Kuuga up to Kiva were standalone. Agito referenced Kuuga in the first few episodes and many people consider it to be a Kuuga sequel, but connections with Kuuga were officially denied at the time. There was also a small Den-O/Kiva crossover which was acknowledged by neither future Den-O movies nor kiva's tv show. Movies made in this period were clear alternate universes, or alternate endings. There was one big exception - Den-O's first movie, which tied in with the tv show.
-Decade brought back crossovers in a major way, but used alternate universes and didn't go into detail about the supposed original Riders, leaving people with doubts regarding its validity. Decade's movie, All Rider vs Dai-Shocker was set up and acknowledged by several scenes in the tv show, but it doesn't have a clear placement within the series. It also heavily used alternate dimensions and dimension hopping. So all the Riders fighting together here doesn't really answer anything regarding timeline.
-W set up a threat which would go on to reappear in the following years and basically seemed the start of a new continuity for Rider, and even had a cameo related to the next series in its final episodes. Its movies, including Movie War 2010, which had a crossover with Decade, and W Forever, which had a crossover with OOO, were all acknowledged by the tv show.
-OOO didn't use the connection set up by W's tv series, and none of the movies made during OOO itself could fit into the tv show's timeline without problems. They were never officially declared alternate universes though. However, meanwhile, W continued getting movies that followed upon what was set up before, like a certain marriage in the W/OOO crossover. Finally, OOO includes a Fourze cameo in its final episode.
-OOO Wonderful was described by its producer as taking place when Date was Birth in the tv series, but it can't actually fit at any point of the tv show. Still, it was acknowledged by the OOO/Fourze crossover, which was acknowledged in the Fourze tv show itself, and the OOO tv show acknowledged Fourze in its final episode... So, it is part of the overall continuity, but can't fit fit into any specific moment of the OOO tv show. This inconsistency was created basically due to OOO's producer not worrying about continuity, while producer Tsukada (W, Fourze) seems to be trying to push this new continuity for Rider.
-Fourze features the past Riders cameo in episode 2, and uses "Kamen Rider" as an heroic name even afterwards, tying in the supposed new continuity started with W to past series. It also takes the same approach to the movies that W had, acknowledging them. The past Riders are the cause of some division among fans though.
-Some people consider only these shows that have gotten cameos in Fourze to be in the same continuity (so, All Riders up to Black RX + Kuuga and the post W series). Others consider all Rider shows to be in the same continuity now, especially due to Fourze's official material just mentioning past Riders, rather than specifically saying that only part of them are in continuity. However, the official material also doesn't say "All past Riders" just "past Riders", which leaves space for people to argue the opposite.
So I want to hear from fans just what are the continuities of the franchise?
Basically, at this point:
-Either there's only one continuity covering every single Rider tv show and standalone movie (aside from the early Heisei movies which were meant to be alternate universes), or;
-There's a continuity covering Rider 1-Black RX, Kuuga, Decade, W, OOO, Fourze and now Wizard, with everything else taking place in unrelated alternate universes (and Decade himself constantly hops universes, so most of his series technically doesn't even take place there).
that and the whole OOO/Den-O crossover. That and where does OOO Wonderful fit into the timeline (if at all)?
Edit: Oh yeah and OOO's 27 and 28 episodes that celebrate 1000 episodes...... Anyone kind enough to explain that bit, please?
You see, for this part, you need to understand some behind the scene issues. The producer who's pushing for this new continuity, like the ties between W-Fourze and the past Rider cameos in Fourze and Megamax is Tsukada. He seems to have some kind of "concept" at least, even there isn't proof that he has an overall plan for the continuity.
Meanwhile, Let's Go Kamen Riders and the anniversary episodes were handled by Shirakura, who was the producer of most of those earlier Heisei shows and movies. Although the anniversary episodes and movie featured past Rider cameos and the movies even had Rider 1 and 2 as main characters, the production behind those movies wasn't really worrying about continuity at all (for example, the depiction of the 70s there has some big differences from the real original series). So, even though it technically features everyone together, most people just disregard it while talking about continuity - and, unlike Movie Wars Core (the W/OOO crossover) and OOO Wonderful, Let's Go Kamen Riders hasn't been referenced by any later productions.
Shirakura's more recent Super Hero Taisen (the Rider x Sentai crossover) actually seemed to try more to fit in with the established continuity that's being built now, but it still has issues (mainly regarding OOO). I think it has larger chances of being acknowledged afterwards though, but that still needs to be done and hasn't happened yet anywhere.
