To me Kuuga to Agito is like Frankenstein Conquers the World is to The War of the Gargantuas. There are some references to it, otherwise you don't need to watch Kuuga to watch Agito.

As far as I know JoJo posing has nothing to do with Tokusatsu, the creator of JoJo loves fashion magazines and copies the poses he likes, or is inspired to make new ones based on them.

But Toku references in manga and anime are a common thing, yes.

It's not a direct sequel; Kuuga is mentioned (not even by name) as the reason Japan prepares to fight monsters in Agito, that's literally it. You could even argue that Agito is not even a sequel at all, since said reference is the only one and no character form Kuuga reappears in Agito.

So you don’t need to watch Kuuga before Agito if you don't want to, but if you want to check out both you might as well start with Kuuga, just to see how the franchise evolved.

Why does every Kamen Rider with a supernatural motif like Kiva & Ghost fail? AND Wizard!?

I personally like all three. It’s all subjective to taste, really. :)

Also, Agito heavily deals with the supernatural, and it doesn't suck at it IMO.

Yeah. It really just depends on who's writing it.

Probably one of the few shows Inoue does not get hated on I guess.

Which series would you say has the best first episode?

I've always found most Kamen Rider shows take two episodes to really establish themselves, so this is really easy to narrow down for me.

Wizard's first episode is a great done-in-one, Gaim's was really solid, and Drive's is an awesome superhero origin story in 22 minutes.

Other than that I don't know what'd even be close. There's memorable moments in plenty of premieres but it tends to immediately get overshadowed by something cool in the next one. Just for example, in Kuuga you've got that whole fight with the helicopter and that's cool and all, but episode 2 is where Yuusuke really decides to be Kuuga, and that fight in the burning church is one of the most memorable scenes in Kamen Rider.

All my opinion, of course.

Black, hands down.