FFIV is a very good game. The good things you've heard about it are right. It isn't anything complicated like the modern games or even FFVII but it's a classic fantasy RPG with a few twists that make it a worthy Final Fantasy title.

FFVI is something older fans tend to cherish more than even FFVII so I'm not surprised at the results. Personally though I didn't see the appeal. I'm actually more impressed by FFV than VI because of the improved Job Class System. I'm surprised FFVIII ranked so low but thinking back the gameplay itself was very annoying so I can understand. I'm much more of a story person as my own topics probably show haha. So FFVIII ranked higher just because I loved all the twists and emotions. Also the icicle to the chest scene was so iconic I suppose that miHoYo even paid homage to it in Honkai Star Rail with Cocolia doing the same thing to the MC.