Okay, so first off I will admit that there are some big holes in my KR viewing - all of them Showa series which are either not fully subbed or cost $150 for the dvds. the only two shows I've seen completely from the pre-Kuuga era are Amazon and Black. That being said, I always find myself coming back to Black as my all-time favorite series.
Black is one of those rare cases in life where a series actually manages to completely live up to its large amount of hype. I went into Black hearing how it was one of the best Kamen Rider series of all time, a dark and serious masterpiece of late 80s tokusatsu, and while I don't think it was necessarily as dark as I'd heard, I can't deny that I found it to be every bit as good as promised. From the first second that we see Kotaro running through the crowded streets of Tokyo in an attempt to escape from the ghostly forms of Golgom's high priests, to that last scene of him sitting around the empty coffee shop remembering all the friends he's lost, it was such a good and engaging show.
I'm not even sure where to begin talking about everything that worked for me in Black. i loved Kotaro; he was a guy who was really put through the emotional wringer during the course of the series, but he never let all the pain and sorrow truly overwhelm him. Even at the end you get a sense that he'll still be able to move forward with his life. And while his extreme (yet highly accurate) paranoia about Golgom was amusing, he was always willing to rush in and face the latest monster head on. I loved the simple elegance of the Black suit and its lack of gimmickry - no fancy gloves, no light saber, no form changing, just a guy beating up monsters with his own two hands, feet, and seizure-inducing strobe effects.
The villains are also fantastic. I love the high priests; the designs, the performances, the overall aura of evil they exude... even when they get upgraded to the super mutants mid-show I still like them, especially since they start getting in there and mixing it up with Kotaro more. The show lacks the traditional Kamen Rider mooks, but the show does a good job of making up for it by having the generals get into the fight more. Birugenia was especially good at it and he always felt like a real threat to Kotaro. And then, of course, there's Shadow Moon. Man, I love Shadow Moon. Yeah, he tended to just stand around the base and send out monsters, but when you heard the click of those boots coming towards Kotaro you knew something major was about to happen. Plus he had such a beautiful design; I love that suit even more than Black's.
The story may be the one area where the show hits any bumps, as it has some serious pacing issues. The basic storytelling engine is solid - Kotaro's brother has been kidnapped and he wants to defeat Golgom to save the poor guy before he gets brainwashed into becoming an unstoppable monster. The problem is that there are entire stretches of episodes where this gets forgotten and Kotaro just goes around saving little boys in tiny shorts from the kaijin of the week. We always drift back to the Nobuhiko plot, but the story was clearly not designed to stretch out to 51 episodes. Thankfully, even the filler is engaging and whenever we get back to the main premise it's always great, especially when we get to that fantastic pyrrhic victory at the end. Black is, in many ways, a complete tragedy, which is pretty rare in the world of Kamen Rider. I'd say only Blade comes close to capturing the same level of tragedy, and even that is more upbeat than the sight of Kotaro sitting alone in the cafe at the end of Black - no Nobuhiko, no Katsumi and Kyoko, not Battle Hopper, no whale mutant, just him and his memories.
Let's see, what else in Black was awesome? Good supporting cast; we only had Kyoko and Katsumi, really, but they were both likable and frequently relevant to the plot. Battle Hopper is easily the best KR bike ever, although I do quite like Road Sector, too. The monster designs weren't the best in the franchise's history, but they were still good. The action sequences were always reliably good. The music... oh man, I adore the music from Kamen Rider Black. The opening and ending themes alone are great, but all of those rock tracks that pop up during the combat are fantastic, as is the slower incidental music. I've got the full soundtrack on my iPod and I never get sick of hearing these songs.
I could probably just sit here all day and keep listing great things about Black. For me it is, hands down, the single greatest Kamen Rider series ever and I do not see a new show ever coming along to steal that title.