I like your feet being visible when you look down in first-person games, I like being able to interact with small background objects (especially in Assassin's Creed, you used to be able to pick up brooms and fishing rods and use them as weapons, but sadly that feature was removed in the latest one), I like being able to choose the posture of my character in an RPG, I like good footstep sounds on different terrain, I like being able to skip cutscenes, but look at them later at my discretion, I like being able to take screenshots (although implementing it through an in-game camera can get a bit impractical), I like cutscene easter eggs (not going to lie, the only time I've seen these is MGS4), I like collectible background intel (Resistance), and I like dialogue being different depending on what your character has done. This last one in particular is, I feel, a chronically underused narrative device that would add so much characterisation and immersiveness if only there was a little more dialogue!
Armored Core, for example, has a very barebones approach to NPCs. Some of them are likable, some not, they're almost always overplayed or 2-dimensional, but they sometimes say different things depending, for example, on how quickly you finish a mission or whether you kill them last if they're an enemy (not so much with the most recent game, but...well, you know). The game would be orders of magnitude better if, say, a certain heavy AC pilot would compliment you when you use tank legs, a cocky LW pilot may ridicule you for it, or say something competitive if you're using LW legs, maybe there could be comments on your use of blades, or an extra line if you've been mainly supporting or mainly opposing their company through missions. Maybe one says "Do you know something I don't? That's some serious weaponry" when you bring a Kojima Cannon to a mission described as mopping up MTs but which you know from playing it is an AC ambush. Maybe if you get too close during a mission, they tell you to back off. Maybe if you have weaponry gained from beating the game once, they ask you where you got it as it's experimental, weapon-depending.
Maybe in Dark Souls, Siegmeyer comments on your armour if you're in full Catarina and uses a particular term of camaraderie afterwards when talking to you, maybe the Firelink Shrine Firekeeper gets a bit nervous if you try to upgrade Estus will a Firekeeper Soul you had to kill a Firekeeper for, maybe Patches doesn't trust you when you say you're not a Cleric if you have over 30 Faith and a Talisman equipped, maybe if you get hit by a boulder in Sen's Fortress the Crestfallen Merchant remarks on dented armour if you talk to him in the same life, maybe Lautrec doesn't tell you you look like a Hollow/that Priestess girl speaks to you more amicably if you're NOT ACTUALLY HOLLOW.
In any case, much broader, more varied, context-sensitive dialogue would make a lot of games a lot better.
EDIT: Oh and not particularly minor, but I DESPISE a) not being able to kill annoying children and b) attacking being only available when engaged it combat. Two things I hated about the last Assassin's Creed.
