So, once upon a time I was obsessed with badly-dubbed children's anime designed to market toys and video games. With a background like that, I obviously know these series have many important differences, and that's why they're named individually. But the reason they are "guilty pleasures" is fundamentally the same for each: I was too old for those series and at times felt every inch of it, but I still went crazy over them.
I realize that a large majority of popular anime is intended for a younger audience than some think it is, but if we're talking pure emotion, it's valid to distinguish between series for children that do or don't make you feel childish for watching them. Even though its intellectually dishonest, this is how I reconcile considering these series "guilty pleasures", with my broader enjoyment of children's cartoons.
It also doesn't matter if we're talking about the heavily-edited dubs or the original versions, either. Yu-Gi-Oh! was the only one of these series that I saw in Japanese, and while it had a ton more gravitas and a better plot in Japanese, it was still pretty ridiculous. Any others, I never got around to watching in Japanese, but I imagine my reaction would be the same.
The reason I liked these series was because they had cool or adorable monsters, liked some character or another, and/or these series unlocked my first feelings of almost-nostalgia, as I got a buzz of being exposed to childish things that I hadn't actually known as a child. My attachments didn't run any deeper than that, but they had strength for a while.
For a few years Yu-Gi-Oh! even became my main fandom. I have no idea why, since my reasons for liking it were superficial and never involved embracing the actual themes and content of the series. I was hardly alone when I did this: there was a notable adult female fandom for the series, but looking back I, personally, still don't get why this happened to me.
And it's maybe because I never got it, that I forgot all about these series very quickly. However, forgetting doesn't mean rejecting. If I happen to run into something related to any of these series, I get a warm nostalgic glow, and instantly accept that I still have a soft spot (maybe on my head) for 'em. I own only fragmented DVD collections, but sometimes I wish I owned more. The thoughts pass, but they always come back.
Yet the best one out of all of these was probably the third Digimon series, Digimon Tamers. Under the guiding hand of Chiaki J. Konaka, a guy who likes Lovecraft and Evangelion and making his own strange anime, Tamers actually had a decent and compelling storyline that had nothing to do with acquisitions or tournaments.
There is still a certain chronological cutoff date for my interest in these properties. At some point, I stopped caring about new product for these media franchises, and I still don't keep up with those of them that are still alive. All of my good feelings are reserved for material that came out pre-2005. There are also other, similar shows from that time that I have completely forgotten about. But there's no fooling me: I still hold a special place in my heart for these series, no matter how much sharper my faculties get.