ABBA did a beautiful thing, making so much music that could be placed into such an elegant, quirky, and fun musical. I had to do a lot of thinking while sitting down to write this, and even now my order is changing, but this is the definitive "Top 10" list for both Mamma Mia films.
PS. A song can be slow and sad and still be considered a jam. There are going to be some sad songs on here.