I've had to think about this but it was kind of fun to take a drive down memory lane. It's highly generational and subjective but thinking about it subjectively:

• Gnome 1 and KDE 2 still heavily drew from Windows aesthetically
• Gnome 2 adopted features from Mac, such as the top bar, but also kept things from windows such as the drop-down application launcher
• KDE continued improving upon that Windows feel, but it has always felt akin

I think Gnome 2 (and probably Ubuntu around 10.04) was the most quint-essentially 'Linux' experience. It's a point where design cues from Mac and Windows were blended and enhanced by functionalities like Gnome Do (based on Quicksilver on Mac, apparently!) and Compiz took it to a whole other level.

Despite being derivative of Windows and Mac, I personally feel Gnome 2 took the experience so much further down their own path that it became a thing of itself.

Basing your experience with Linux solely on pop culture/media then you'd likely see any low-footprint twm like i3wm as the most linuxy linux to ever linux. That would be a valid argument, as would something like OpenBox.

Tiling window managers are a great extension from tiling terminal emulators.

OpenBox brought out the concept of not having bars top and bottom and made the desktop feel that little more open. It did strong encourage the use of it's cascading windows though as you had to right-click the desktop to open anything (without further modification).

Personally, Gnome 2 and OpenBox are what I believe are the most quintessentially "Linux" feels in my mind when I consider, objectively, how dissimilar they were to WIndows or Mac.