Though I wasn't a fan of the ALO or GGO arc, the Mother's Rosario arc was definitely the highlight in SAO for me. Very beautiful. The ED was what struck to me the most. I love the chorus and the techniques used. Not to mention, LiSA's beautiful voice.
Another song I deeply enjoy would have to be "Mirai" which was used to promote the Manga, and the live-action adaption of the manga, "Orange". I just finished the manga, and wow, the art and story was very interesting.
This is definitely one of my go-to songs. It starts of with a beautiful piano playing, then goes to the first verse. Very beautiful. The song is "Hyakunen no Koi" which translates to "A Hundred Year Love". I can see this playing in Tomoyo After (maybe if Lia sung it).
This is my sleep song :3 The melody is just beautiful. Thought the lyrics are depressing, I don't read them and pretend that it's about something happy. The song is "Ikanaide".
The next song is definitely, one of my favorites. I think I had been obsessed with this song for a while now. There's a piano version to this, but sadly, I can't find it. So here's the original. Still gorgeous though. Note - Song starts at 00:15. The first 15 seconds is just random guitar melodies. This is "Kimi ha Kureta Natsu"
One of my favorite songs is definitely "Save Me". It's a very beautiful song. I think the chorus, verses, everything, is just beautiful.
This is the final song. It's a Korean song, but the melody, the vocals, and everything is just perfect. It's not something poppy. It's just mainly them and a piano. Definitely worth watching and hearing. This is "Eyes, Nose, Lips" by Taeyang, but the Fantastic Duo version.
I hope someone found something they liked in here.