I can't really say much about DC as I had only watched Wonder Woman, but here is my top 4 from the Marvel Cinematic Universe:
1. The Avengers
2. Captain America: Civil War
3. Black Panther
4. Spider-Man: Homecoming
Same when it comes to DC
Here are my top 4 favorite Marvel movie... and here are my top 4 least favorite ones...
1. Spider Man Into the Spiderverse (This doesn't limit to MCU movies right?)
2. Avengers Infinity War/Endgame
2. Black Panther
3. Guardians of the Galaxy
4. Spiderman Homecoming
Least favorite:
1. Captain Marvel (Oh boy, the sjws and feminist are gonna bash me lol)
2. Ang Lee's Hulk (Really hurt for me to put on this list because Ang Lee and I are both Taiwanese so I like him a lot, but man his Hulk movie didn't age well)
3. Avengers Age of Ultron
4. The Amazing Spiderman 2