I thought it was one of Pixar's best movies. It made me cry a lot.
Naturally, the movie is incredibly symbolic and metaphorical, since it takes place in the mind, so I thought it was interesting that each person had a different emotion in charge. Sadness was at the forefront of the mind of Riley's mom, while Anger gave out orders in the mind of her dad.
I thought it was also clever that the emotions in her parents were all coordinated and dressed the same, while Riley's emotions all had their own unique style.
The most amazing part of the film, for me, was when Sadness began to take center stage. It was an eye-opening moment, and Joy really put my feelings into words when she began to have the same epiphany as me about the importance of sadness.
Upon further reflection, though, I realized that each emotion serves a similar purpose in the sense that it helps people gather support in different situations. This NY Times article that theNiliad shared elaborates a bit on this, and mentions that Anger is what helps people come together against injustice or unfairness. But each emotion helps people come together in different ways. This is my take on it:
Joy can help people come together in support of something exciting and fun.
Sadness helps people come together over grief and loss.
Fear can help people come together against something new and potentially dangerous.
Disgust can help people come together and collectively avoid toxic and unhealthy people, places, and objects.
It's unfortunate that we couldn't see the full gamut of emotions that are running the show in reality, but that would've probably turned into a TV sitcom rather than an hour-and-a-half long kids movie.