Can Gorenger really be cited as "Starting it all" when it wasn't even counted as an official Sentai until the 90's?

It's like citing Gatchaman, because, without Gatchaman, Jetman wouldn't exist...

everyone mentioning syuranger and the sixth ranger, what about the mechs, the improvements made on that alone make it importanr

True. Zyuranger was a massive improvement in mech suit design, especially if you look back just one year to the blocky flat boxes that made up Jet Icarus.

Most important Sentai ever, though, is Dekaranger. Because it gave the world Umeko.

It's not super sentai, but it was basis material to a certain degree :)

Where would you guys say "Neo-Heisei" if you will, started for Sentai? Go-Busters perhaps?

I tend to go with this breakdown, which marks the current era of Sentai as starting with Go-Onger: http://tokuwarriors.blogspot.com/201...even-eras.html

I see Turboranger as the start of phase 1 Heisei since they are the first Heisei team, from Gaoranger onwards phase 2, and starting from Go-busters phase 3.

That's what I mean.
Can Gorenger be cited as the start of a franchise when said franchise didn't even acknowledge it for well over a decade?

King Ranger from Ohranger was the first with kanji on his helmet, but I get the idea of what you are saying. Every season offered something new and different