Like everything Intro to a show is massively subjective. Whats good to me in an intro is that the music gets me pumped for the show and the visual gives you an idea of what you are about to watch.
Since im first i get to go with the ez picks, my top 2.
GitS second gig
Attack on Titan season one
Im curious about everyone else. I could post more of my fav, but i hope people surprise me with stuff i know nothing and the intro pumps me into watching it. PS i included comics as well, if i went for my TOP 3 the original X-Men comic was in there too.