3DS was really the sweet spot for me. Simple, charming, clean, and concise. A natural evolution from the UI and formatting of the DSi. Many of the system themes were charming and creative--not to mention the themes I could get from homebrew software. I loved downloading themes based on old Disney movies I used to watch, or non-Nintendo games I grew up with. It was smart, without being too complicated or safe.
I haven't really liked anything past that. Modern Xbox and PlayStation UIs are much too busy and littered with advertisements, and the Switch UI is as devoid of life and personality as an interface can get.
There was a charm in pre-menu systems as well. The feeling of clicking a cartridge down in my NES, closing the flap, pressing the button in and watching the static wash away to wonderful chiptune music... those were the days!