I know a lot of people love TS2 as the best movie and think it's better than the first one but (as you read from the title) it's the other way around for me.
Nostalgically, TS1 is the best film because I have a soft spot in my heart for Andy's room having that classic white cloud wallpaper, especially with that Buzz Lightyear asthetic (never cared for the cowboy decor).
I remember around when the first movie came out, they did a lot to promote the film. I remember watching on ABC Saturday Morning ABC aired 10-30-second shorts and them being so much fun to watch! Including the army man chants when coming out of and going into commercial breaks! They never did those for TS2. The shorts were called Toy Story Treats and IINM, Pixar produced 52 of them. But the "episodes" are so short that it feels like less.
When Toy Story 2 was being released, I was disappointed as a kid that they changed the wallpaper because I felt the white clouds look so much better than the yellow stars and that's actually an opinion I still hold today. But I think the switch to the yellow stars makes sense. One: Andy's family moved to a new house and two: Andy kind of outgrew the white clouds at that point.
However when it comes to the actual plot and between the first two movies, I still prefer the original over the second one all day. The story of the first film is more appealing to me.
My best-to-worst order (and there is no "bad" TS movie, really) is: 1, 3, 2, and then 4.