Winter. I've been tempted to time travel there a few times, but I'd rather just wait. It's so pretty, and I can't wait to see it in NL for the first time <3
I actually love Spring. I loved seeing the cherry blossom trees in Spring in the older games, and I'm really starting to like Summer in NL due to its abundance of pretty new insects (I've fallen in love with the birdwing butterfly.) I've seen screenshots from a TTing friend of the aurora in winter, though, so maybe that opinion will change!
Winter. I love when the trees have their lights for Xmas, and I can't wait to see my perfect apple trees covered in snow. Add snowmen and igloos and snow falling in 3D. Can't wait!
Not sure yet since I've only played in spring and summer, but I imagine that I will like autumn or winter the best since those are my favourite seasons in real life. ^^