It really depends on what games the two of you like.
Divinity Original Sin 1 & 2 are amazing for co-op, they are story driven tactical RPGs. (Local co-op)
These are not local co-op but still posting them for others. You can play DarkSouls in co-op, taking turns being summoned into the others world. Dying Light goes on sale pretty cheap all the time and you can co-op trough almost all of it. Risk of Rain 1&2 (Risk of Rain 1 has local co-op if I remember right) Orcs Must Die 2 was a fun co-op tower defense from several years ago.
Also the current indie Nordic hit is Valheim a game that is much better together than alone.
(post is archived)