Isn’t Fourze really kid-friendly for a reason, though? Because it was made in 2011 when they wanted to do something for the kids who were afraid and sad at the time? I heard something like that, and if that’s the case I can’t blame Fourze.

I never even really found Fourze to be particularly kid-friendly as in, not more than W or OOO. It's very light-hearted, but that's about it. And yeah, Fourze was made after the disaster of the Tohoku earthquake and the accidents in the nuclear power plant at Fukushima.

I think Den O is pretty well liked by most toku/KR watchers.

This is just what I remember hearing from some of the ratings gurus at the time: Fourze was a big hit with kids, but the older fans - the guys who spend a lot of money on Figuarts, SIC, and collector's belts - really didn't like it.

Personally, I like the show a lot. It's one that I actually find myself liking even more in hindsight then I did when it was airing (probably because my brain is blocking out most memories of Yuuki).

I think Fourze's lightheartedness really did it favors. It was fun, pure and simple. It did have it's deeper plots, but it didn't dive into the melodrama like Den-O did, only just kind of dipping it's toe into that pool.
While there are fans that didn't like it's gimmick, I think opinions on the show lean closer towards the positive.

Fourze seems like it would be popular in Japan to me. I get the backlash against it's lightheartedness but still, it seems popular enough among the English fans.

If we're objectively trying to determine universal appeal, though, we have to consider every opinion. If you start weighing opinions on a curve, objectivity tends to go out the window.

I disagree.
Black was meant to be a back-to-basics since the planning phase and folks that like Black seem to like it for that reason.
As for Kuuga I do agree it was experimental but out of those experimental bits came some new standards from what I see, such as the cinematography and mise-en-scene.
And all this talk about Black makes me want to watch it again.

*shrugs* Eh, He was an excellent doormat.
The Rider Battle was such a fresh concept for the franchise circa 2002 and I remember people loving the show for it at the time.
And while we are on the topic of doormat, this was hilarious:lolol
http://i.imgur.com/RZZO5re.jpg

No, that's not what I mean. I'm not saying that opinions in Japan weigh more than others (ok, maybe I did say that my phrasing was poor) I'm saying if we're considering every opinion, most of those opinions are probably gonna come from Japan because that's where most fans are gonna be.

Still, that's not really what universal means. I think if something has very different receptions in different parts of the world, that means it's not universally liked.