When I was between the ages of eight and twelve, 50% of my time was dedicated to Spore, so I always say it's my favorite out of nostalgia. I also really like Undertale, Night in the Woods, Super Smash Bros, Hollow Knight, Terraria, Splatoon, and Pokemon.
Star Wars Galaxies was my first online obsession. City of Heroes and AION were also a lot of fun for the flying parts. More recently there's Warframe, which my avatar came from, though I haven't really played in months.
I like city builders like Forge of Empires (browser), Planetbase, and Frostpunk. Watching "ants" do their thing and planning things out is relaxing.
Also survival/builders like Don't Starve, Subnautica, and Rimworld.
Current favorite is Beat Saber because who doesn't love light sabers? It also doubles as exercise. The Rift is the only piece of exercise equipment I've bought that I actually use regularly.