The GTA games have been my go to comfort games since at least GTA IV, but very much solidified in GTA V.
For IV, I'd grab a completion save, mod in a 1st person view. GTA V I had to beat on my own, but in either case, afterwards I'd just...walk da earth.
In both games, I just...wander around. Just get out the house and wander. Didn't matter where. Both games were big enough that I'd always eventually stumble on someplace I didn't know about before. VI was less accommodating on the vehicle side of things, what with it's much crappier traffic AI and all-urban terrain. But V...man I've clocked in...well, let's check out Steam...
Over 300 hours. Only game on steam I've played more of is Left 4 Dead 2.*
Only a paltry sum of that was actually 'playing' the game. I'd spend hours, walking, driving, doing nothing but just...being in the game. Turns out there's actually very very few games where you can do that. Where just being in the game world is a satisfying experience. I couldn't even do that in Skyrim...and I put over 500 hours in that sucker, it just don't show on steam cause I used a cracked version.