I watched Guardians of the Galaxy Vol. 2 with my daughter tonight.
She absolutely loves this movie.
From Baby Groot in the beginning to Drax getting swallowed to by the big monster, Drax getting slammed by trees, Cartoonish faces when warping and Baby Groot throwing up, all the way to the Ravager Salute for the funeral and the silly faces in the initial credits at the end.
She actually got up and started dancing during the credits. To be honest, she was quite animated and active during a lot of the movie, it was so many scenes she was into, I can't quite recall them all off the top of my head.
I do know Baby Groot was by far her favorite, dancing, throwing up, not understanding the request, chasing down enemies, I think she loved every scene for Baby Groot.
And surprisingly, she was following the story just fine w/o me having to really explain much of anything.
So I would have to say, just from observation, that this was her favorite movie in the re-watch so far. She was laughing, dancing, re-enacting, joking, and just enjoying herself for the majority of the movie. She was not only following along, but telling me what I had missed in the story, as I had to leave the room several times after we started watching.