Kamen Rider is a long-running superhero tokusatsu (basically "live action with special effects") franchise created by Cyborg 009's Shotaro Ishinomori and run by media conglomerate Toei. There were several shows and movies scattered through the late 20th century, but since 2000 it's aired on Sunday mornings alongside its sister show Super Sentai, the source material for Power Rangers.
Both shows get a new "version" every year so Toei can sell new toys to new kids (and you really need to remember when evaluating them that these are shows for children). They're disconnected from each other apart from the traditional team-ups and crossover movies, so you can evaluate each show on its own without worrying about continuity. They tend to follow similar plot beats and structure, so whether you enjoy any given season is up to personal preference.
Keeping in mind that I've only been watching these shows for a few years myself (I've only seen like maybe a quarter of the total number), here's a couple starting points.
Kamen Rider Zero-One (2019)
Humanoid robots called "Humagears" - designed by the AI corporation Hiden Intelligence and coordinated by the AI Satellite Zea - are an accepted fact of life and integrated into all levels of society. When the president of Hiden Intelligence passes away, the terrorist organization Metsubojinrai.NET commences their plan to hack Humagears and transform them into monsters with the goal of wiping out humanity. As a fail-safe, Zea creates the Zero-One Driver, allowing Hiden's president to transform into a Kamen Rider to combat this threat... but with the president dead, the duty falls to his grandson: a washed-up circus comedian.
Pros: Clean suit designs, strong supporting cast, charismatic villains
Cons: Hero's gimmick is making bad puns, the onset of COVID cut the show short
I've got a soft spot for Zero-One because it was a breath of fresh air after four years of shows I didn't like. Its kids-show-level examination of "AI! Robots!! The Singularity!!!" probably doesn't play quite as well now in the era of every single corporation trying to push LLMs, but as a basic "are robots people??" story it works fine. Also, it really does have some of my favorite villains in the series.
Kamen Rider Kuuga (2000)
Archaeologists unearth an ancient sarcophagus, awakening a warrior tribe called the Grongi. Capable of masquerading as normal people, the Grongi immediately resume vying for glory and leadership in the form of a twisted game of murdering humans via increasingly cruel methods. Stop me if you've heard this one before: only the ancient warrior known as Kuuga can stop the Grongi, and his essence has fused with a normal man who must now take up the mantle of Kamen Rider.
Pros: Nowhere near as toy-driven as the rest, relatively serious in tone
Cons: Cops, slow pacing, not much of a metaplot until the final third
What if Kamen Rider was a police procedural? Kuuga has the venerable position of being the first modern-era Rider and the bedrock upon which the current blueprint of the series is built. It's still got one foot in the previous century, which lends a sort of charmingly old-school feeling as the crew feels out out how to do a 21st-century Kamen Rider.
Kamen Rider Geats (2022)
The Desire Grand Prix is an extradimensional battle royale where entrants become Kamen Riders to compete in various games and events. Winners of the DGP are awarded the privilege to remake the world according to their greatest desire. It becomes clear that the enigmatic Kamen Rider Geats has not only competed in but won the DGP multiple times, and yet he continues to desire something the powers-that-be can't - or won't - provide.
Pros: Rotating cast of wacky entrants, solid Rider-vs-Rider premise, fun power-ups
Cons: Crumbles into a morass of plot twists by the end, game theming can get obnoxious
The Kamen Rider series as a whole has trended away from monster-of-the-week and towards Riders battling each other, so 100 Riders dropping onto an island was a natural choice to be hip with the kids. I'm sick of "video game mechanics" cropping up as a plot device everywhere, but Geats makes it work by building the entire premise around it.
Kamen Rider Black Sun (2022)
A miniseries reboot of 1987's Kamen Rider Black. Decades after transforming animal people called "kaijin" appeared in Japan, racial tensions are at a peak. After teen activist Aoi Izumi gives a speech at the UN advocating equal rights for kaijin, the reigning political party in Japan attempts to have her assassinated. In the process of carrying out the hit, kaijin Kotaro Minami discovers that Aoi possesses a Kingstone, an artifact related to the origin of kaijin.
Pros: 10 episodes instead of 50, tonally grim but retains the inherent camp of tokusatsu
Cons: Incredibly ham-handed racism metaphor, status as a reboot means some plot points come out of left field
I can appreciate when a show takes big swings, even if it only lands maybe half of them. Black Sun toes the line of good taste with its well-meaning but clumsy attempts at depicting modern-day racism and discrimination, but it's also willing to hold the establishment in clear contempt with thinly veiled caricatures of actual politicians and understands there cannot be a peaceful solution when those in power profit from your pain.
Kamen Rider Fourze (2011)
Pompadoured transfer student Kisaragi Gentaro just wants to make 100 friends, but blunders into a battle with the Zodiarts - monsters who channel the infinite cosmic energy of outer space - on the first day of school. Good thing there's a wormhole in one of the school lockers to a secret moon base containing mysterious technology that allows Gentaro to transform into a Kamen Rider and protect the school!
Pros: Written by Kazuki Nakashima (Gurren Lagann), is extremely dumb
Cons: High school, supporting cast is hit or miss, is extremely dumb
IMO tokusatsu is at its best when it's embracing the inherent silliness of having guys in rubber suits punching each other, and Fourze's overtly comedic approach works wonders. It's directed by Koichi Sakamoto, who did stunt coordination on Power Rangers for years, and his approach to choreography and physical comedy is probably the best in the biz. Also notable is that while Fourze is set in high school, it's specifically taking on American high school tropes with football jocks, cheerleaders, goths, et cetera, which has its own goofy charm.
Kamen Rider Gaim (2013)
In the stifling corporate town of Zawame City, teens have formed competing dance crews as a form of social rebellion. Part of their competitions involve summoning creatures called "Inves" to battle each other, and rifts are starting to open to a mysterious forest encroaching on reality. When an Inves eats a fruit from this forest, it evolves into a more powerful form, and the fruits also power transformation belts that have begun to spread throughout the city. The Yggdrasil Corporation patiently watches on as various factions scramble for an advantage and vie for power...
Pros: Actually has solid characterization, stakes, and themes compared to literally any other mainline TV Rider show
Cons: Gen Urobuchi has never been able to write women and he ain't starting here
This is the first Kamen Rider show I watched and it kind of ruined me on the rest of it. The intrinsic silliness of fruit-themed samurai dudes fighting each other and the limitations of being a 24-minute Sunday-morning kids show curtail most of Urobuchi's worst tendencies while allowing his skills to shine through. This does also mean you should probably skip any of the episodes he wasn't involved in.
