For the 20th anniversary (I started before, ended after), I rewatched Power Rangers. All of it. Every episode (plus the canon Turbo movie). In order.
Now, it should be said, that a) I never watched every season before, so some of them I never had nostalgia for, and b) I
do like some Super Sentai series, as an adult.
Mighty Morphin (1-3): Wow, these were so much cheesier than I remembered. Not to the point of unwatchable, but I could only do a few episodes at a time.
Alien Rangers: I'd barely remembered this mini-arc (that I had to hunt for, since Netflix a) lists it as its own title, and b) it doesn't come up on a search for "Power Rangers"), but it's pretty standard with the rest of Mighty Morphin.
Zeo: Same as Mighty Morphin.
Turbo: Had to track down the movie at the library, since it's not on Netflix. Not sure I'd ever actually seen it before. As for the series, as a kid, I loved Justin (probably because he was near my age). As an adult, I see how it really didn't work. Not the having him as a ranger part, but the "oh, this kid's in high school and not really bullied and hangs out with recent graduates" part.
In Space: This one was about as I remembered it. Not as cheesy as the ones before, but nothing to write home about, either.
[space here, since the rest are (mostly) stand-alone, and not one ongoing series]
Lost Galaxy: Growing up, Lost Galaxy was one of my favorites. Watching it again, I could see a lot more of the flaws. I still enjoyed it, but not as fondly as I remember.
Lightspeed Rescue: When I was a kid, my favorite thing was seeing characters my age (or close enough) doing cool things. That's why I liked Justin in Turbo. That's why Jubilee became my favorite character in X-Men (she's still one of my favorites, but there are others... all around her same age ^^;
. So when LSR started, with adult characters, it turned me off. I got a couple episodes in, but never finished it. Watching it as an adult, I liked it a lot more. It's not a standout series, but it's definitely a step above the 90s cheese that was the first set of series.
Time Force: I'd caught bits and pieces of this one, but not very often, so I can't compare to what I enjoyed as a kid. But I'd liked what I'd seen, and I did enjoy it. I can definitely see parts that were sub-par, but it wasn't bad.
Wild Force: This one I went in cold to. I'd never seen any of it. I also hated it. I may have enjoyed it as a kid, but I'm not sure. The whole "we're gonna kidnap this guy and force him to be our red ranger" that bothered me as an adult, I probably wouldn't notice, but Princess "i.am.a.robot.with.no.emotion" Shayla would have annoyed me just as much.
Ninja Storm: Ninja Storm was my favorite of the series as a kid. And it still is as an adult. Having seen all of Power Rangers (with the exception of the most recent series, as it's just recently been put on Netflix and I'm working my way through it), I can say that it is, hands down, the best series. It holds up that well. As a kid, I loved the well-developed characters, the goofy villains, and, yes, the guinea pig sensei. As an adult, I can see that it hits that hard-to-find perfect blend of drama and comedy. The story works well, with no glaring plot holes that weren't explained. There's humor there that goes above the kids' heads, without being crude. Overall, it's a well made show.
Dino Thunder: I liked Dino Thunder a lot as a kid, too. I think part of it was Tommy, who had been one of my favorites of the originals, too. Dino Thunder doesn't hold up as well as Ninja Storm, and when you look at it with an overall storyline in mind, it really doesn't make sense that Tommy got a PhD
and had worked with this guy for a long time, only about 7-8 years after graduating high school. But it does have a great theme song, and my favorite single-episode of any Power Rangers series: Lost and Found in Translation (in which the rangers find a badly-dubbed episode of a Japanese show "based" on Power Rangers... yes, it's an episode of Abaranger, which DT was based on!).
S.P.D.: Another one I hadn't seen at all, but at least this one was passable.
Mystic Force: I'd caught random episodes of MF, and it had me intrigued. In fact, my interest in the storyline, and the outdated notion that "the Japanese version is always better" of shows got me to download Magiranger. I didn't get 2 episodes into Magiranger. Watching MF as an adult, I think that the overall story was good, but the execution wasn't there. The manager of the music shop
couldn't be that dumb, and a lot of the characters fell flat. It just didn't work, although the story rewritten for adults could be really good.
Operation Overdrive: Before my marathon, MF had been the last series I had seen any of (other than a couple random episodes of RPM, shown to me as an adult), so I was going in blind. Well, not quite. I'd been warned that OO was a piece of crap, and to avoid it at all costs. I really and truly wish I had.
Jungle Fury: After OO, nothing could be as bad, so I really can't judge JF on its own merits, because I may just be remembering it as better than OO.
RPM: I'd seen a couple episodes of RPM. Most notably, the beginning of episode... 11, I think, where they basically lampshade all of the common PR tropes, which was hilarious. It's definitely one of the better series, but I do think it fails in that it skews a bit higher in the demographic. Whereas NS was fine for both younger and older kids (and adults), I'd be cautious about showing RPM to younger kids.
Samurai/Super Samurai: This one was pretty bad. I would have probably enjoyed it as a kid, but as an adult, it was bad.
Megaforce: This is basically a remake of the original, although not as cheesy. I know without a doubt I would have enjoyed it as a kid.
Super Megaforce: This is listed separately from Mf because I've seen Gokaiger, which they adapted for it. As a kid, I probably would have enjoyed SMf. As an adult, it was impossible for me to enjoy SMf, because it's a complete bastardization of Gokaiger.