Broadly speaking, I enjoy stealth in games as long as it’s implemented correctly and doesn’t break the game or function poorly and leave you at a disadvantage. Despite the many qualms I have with tlou2, the added mechanic of going prone and all the upgrades associated with stealth was quite fun—and, of course, the functionality of the bow and arrow, and how you can conserve ammo. Parsing an area with dogs and navigating their heightened scent through long grass and deciding when to pick off certain enemies or ninja though is tremendously fun for me.
Desperados III and Shadow Tactics are two other stealth games that I love that use a design similar to The Commandos series. You can navigate through their detailed environments deciphering a path through on your own, using whichever abilities your party has to your advantage. I think the ninja/feudal Japan game world fits better with Shadow Tactics (I also prefer the characters) but Desperados III has just as good, if not better level design.
To add a somewhat weird one, I’ll say a good save feature. Saving with an ink ribbon in RE was so freaking awesome—especially in regards to how it adds a level of complexity to item management. Another cool example that doesn’t add anything to gameplay but was neat: ICO and how you save your game with Yorda on the couch. So wholesome; I can hear the music in my head, even.
E: Also, Demon’s Souls’ character and world tendency mechanics were so incredibly imaginative. The fact that you can unknowingly die too many times in human form, turn an area into black world tendency, and get eviscerated by black phantoms for seemingly no reason is wildly brutal and awesome.
@Zagorath I did but I couldn’t get into it and quit so early that I didn’t even see the save function.