In the main field, I look for a lot of the same things as others with games.
Gameplay is number one. A game with really fun gameplay and horrible will survive longer than a game with aggravating gameplay and a great story. You can ignore story, you can't ignore gameplay. The original Destiny is a great example of a game with horrible story surviving solely on gameplay.
Story/Atmosphere are number 2. If gameplay keeps a game floating, the world is what can take the title to the stars. A wonderful (or horrible depending on the theme) can make slashing badguys work into a bigger picture lead by interesting people, which makes you want to KEEP slashing badguys, not that you need the persuasion!
These are the two big pillars, but they are supported by many smaller facets.
Some smaller things I have that can tip the scales:
Sandbox gameplay; I love being able to do things my way. Scouting out my options, choosing my approach, and having the world react unexpectedly to my actions.
Map Editor/SDK; I like to create my own things in a game, and when the game has been beaten enough, I like to see what other people create. New playspaces, quests, items, weapons, characters. I love to mod my experience to suit my interests and likes. Hell, I have at least 300 hours in ARMA 3 (probably more) of just using the map editor!
Music; If story turns you boat into a rocket ship, music is the booster rockets that get the game out of the atmosphere.
Equipment Variety/Character Customization; Just like I enjoy approaching things my way, I enjoy having the equipment and look I like. Whether that's a High Speed Low Drag military operator, full of giant armor plates, or in a puffy Renaissance outfit, I like the choice to be up to me!
This one ties into above; Beast Races; Call me what you will, but after playing many a game, being a human is BORING. I play a proud Sangheili in Halo, a Khajiit in skyrim, and even a fox sniper in New Vegas. Sadly this option is rarely a factor in most games, but that looks to be improving with Biomutant and Beyond Good and Evil 2.
So those are some of the things I look for, personally.