Glad to have asked this question! A lot of interesting aircraft I never knew
existed and great pictures, I bet they sounded great too
I looked for Soviet behemoths but it seems they quickly pressed on with turboprops after the war eg the IL-18's and took a while to consider really large passenger planes. The DC3-like IL-14 was the largest I found
Re: the piston engine. Apologies yes I was thinking of 4 cylinder Lycomings in today's small passenger planes being cheaper than perhaps a turbo prop in the same plane, not the large radial engines that powered those beasts! I should have made it clearer I was thinking about very small passenger piston aircraft
One piston still flying today is the AN-2 which I think has 10 seats and theres a large Cessna or two. And some bush planes
But I'm not sure which of them carries the most pax... ?