I have played and enjoyed every single Final Fantasy game. Even XIII has some great stuff going for it. The series strong suit is that it’s never stale. Each game is a fresh, new take on a somewhat familiar net of design philosophies.
My favourite is XII. I love its job and gambit system, as well as the world design and music. IX comes just a tiny bit short, then V, probably.
I like the trend of invisible UI. It keeps the display free of clutter and persistent UI elements (hello, OLED) and doesn’t hinder usability at all. I hide scroll bars whenever possible because middle clicking is far more convenient than click-dragging. Hidden elements always appear by using a related action–moving the mouse reveals the play bar, scrolling reveals the scroll bar. It’s completely intuitive. I even remove the forward, backward and reload buttons on my browser because gestures and shortcuts are just faster.
UIs are near-universally as clean and functional as ever… at least on macOS. Windows appears to be a clusterfuck. Linux is alright.