Welp, I've actually started something of a marathon.
I have determined that I must watch every single first two episodes of all the Showa Kamen RIder series, and after that watch what else there is of 'em.
Thus far I have seen
Kamen Rider Original: Sadly only the first episode is subbed, to my knowledge, so I've just seen it and the first Kamen Rider 'movie', based on episode 13.
Kamen Rider V3: Finished watching it last night actually. Fantastic show.
Kamen Rider X: Seen the first episode yesterday due to the subbing group, will watch the rest today, seems to be a very good show, very solid and well made.
Kamen Rider Amazon: I saw this earlier actually, loved it. Very different though, compared to other Rider series.
Kamen Rider Stronger: Currently on episode 4. It's also....rather different. The fighting seems a bit less...violent some how. Not sure. Going from this to V3, there is a marked difference.
Kamen Rider Sky Rider: ....um...I'll get to it. Skyrider is the one Rider I'm...not too interested in watching. But I'll watch it.
Kamen Rider Super1: Watched it a few weeks ago, pretty interesting set up, rather gimmicky, but hey.
Kamen Rider BLACK: Own it on DVD and have the Century King Subs. I freaking love this show.
Kamen Rider Black RX: I do not love this one as much, but it has been watched.
SO I'm basically just missing watching some more X (Woo!) and watching Sky Rider(...great...)