Not really sure what is underrated or not. Only scenes off the top of my head that are sort of "revered by the consensus" are FF4 twins sacrifice, Aerith's death, FF6 opera scene, FF6 Kefka destroys the world, and, probably a handful of other FF7 scenes, etc. Maybe the FF10 and FFT endings? Rydia's return? (almost all the aforementioned are among my personal favorite or respected scenes, as well)

But for me, I personally love the Kimahri vs Biran/Yenke scene at Mt Gagazet. Literally brings me to tears sometimes.

I also really liked both Irvine's introduction and failed assassination scenes. I feel like these are sorta underrated by general FF fans? I dunno, really.

Also, Guy talking to beavers. And Red XIII's first scene w/ his petrified dad (if that doesn't count as one of those handful of FF7 scenes).

I'm sure there are tons of minor scenes, moments, and dialog bits with the Figaro brothers, General Leo, Quistis, and Fran that made me love them so much, that I just can't remember in detail lol.