The first that comes to mind for me is The Breakfast Club and I hope it never does have a sequel or remake
The Princess Bride is another good one
Edit: another one of my favourites is Wall.E, my favourite Pixar movie. There are also several other Pixar movies that don’t have sequels or remakes yet
Blade Runner 2049
I really hope they make one, as I believe this sequel was better than the first one and hope that they will keep up the good work