1. Rythm of War. Honestly, this is mostly because of Kaladin. My favorite character overall. Some of the book might have been a tad depressing, but the ending more than makes up for it. Kaladin swearing the 4th ideal was one of the best moments, other than him swearing the 3rd ideal. And Adolin somewhat restoring Maya over the course of the book was amazing.
2. Words of Radiance. I just loved the 3rd Ideal swearing, and Kaladin coming to terms with his power, but him unbonding Syl and losing his powers does push this down a place.
3. Way of Kings. The first Book is usually one of the best, and this is no exception. Brandon Sanderson is one of the few authors I Know who continue to one up themselves throughout the series, making it continually better, instead of the series fizzling out.
4. Oathbringer. A great book, but jut not my favorite. Keep in mind, these books are very close together. I love them all. I just love some of them a bit more than others. Oathbringer is still an amazing book, i just don't find it to be my absolute favorite.
These are just my opinions.