There are a few super relaxing indie games that spring to mind: Flow, Flower and Journey (all three are by the same awesome dev). I also find Skyrim pretty chill, as well. Just walking around Skyrim is super meditative and calming. PixelJunk Monsters is also a pretty relaxing game on PS3/PS Vita. A new one is out for Switch/PS4 too but it's not quite as fantastic.