I can't really go with my most hours played as that's a mod in a game, so off top of my head in no real order:
Alien Isolation - the best Alien game made, doubt it will ever be surpassed. Atmosphere is perfect, frustratingly difficult at times and felt exhausted by the end, in a good way.
Subnautica - in triple digit hours on this, haven't even finished the story, just loved exploring and constantly finding new stuff.
Satisfactory - hard to describe why this is so good, just the satisfaction of getting things perfectly balanced in a massive sandbox and imagination is pretty much the limit on builds.
Red Dead Redemption 2 - obvious reasons.
PUBG - while it's been run into the ground and I detest it now, the first 18 months was some of my most enjoyable MP gameplay I can remember since Planetside 1.
