Games I come back to often aren't necessarily comfort games for me. I just really enjoy them. Tenchu, symphony of the night, Megaman X4, Megaman legends, Demons Crest, Sekiro, Bloodborne, ff7, mario 64 etc etc
Comfort games for me are ones that pick me up a bit if I'm tired/down or upset/angry about something, like op said. Something to help me get a bit of zen. Mine have evolved over time, it used to punisher on the pc. Smashing enemies in the face and scoring top points was therapeutic at the time lol.
Currently my comfort games are:
Dungeon of the endless
Kingdoms (most often Two Kingdoms)
Shadow of Memories/Shadow of Destiny
Umihara Kawase (SNES)
Vagante / Noita - (lonesome, solitary, slightly slow-paced / careful dungeon exploration.)
One that I don't play myself but enjoy watching a friend playing is OMSI 2, a bus driving sim. Sometimes just "catching the bus" can be very relaxing which I also sometimes just have on in the background while I work / do chores.