I picked Spiderverse because I feel like it would be the most rewatchable, though GoT is a pretty big contender in that point because there's the most of it, even with just a final season. But I know if I only had one to watch, and could only watch one ever, I'd probably want something lighter.
For the record, here's my anticipation/order I most want to see if I have all four:
GoT
Joker
Endgame
Spiderverse 2
Honestly, Joker is probably really tops for me because I want to see JP drop those dank ass beats so hard, but also I don't think I could give Todd Phillips a top spot, tbh his attachment has me very fearful since he's a pretty prominent name in awful #FBC and the material here could potentially play right in to that.