Randomness, if a Diablo style loot system(just complete insanity in modifiers) is done right I absolutely love searching around for the absolutely perfect variant of a weapon, whenever I play BL1 I'm always hunting around for the upgrade to my old standby lucky 7's masher.
Easy to understand mechanics, I actually tried to play Star Ruler 2 at one point and the mechanics were so nebulous and badly named(I still have no idea if pressure is a good or bad thing at this point) I guess this is more down to information given to the player and tooltips.
More "Helpful" less "handholdy" tutorials, By this I mean that everybody at this point should know that right stick moves camera, left stick moves your character, if not they should RTFM or learn to just start randomly pushing buttons on their controller to see what happens. BUT a lot of tutorials won't tell you weird hidden mechanics, obviously I wouldn't expect every game mechanic to be explained completely but a TON of RPG's have all kinds of their own shitty names for "strength" and "intelligence" and they won't tell you what they do. This wouldn't make me mad but generally in the same tutorial they'll tell you how to look up and down but not that.
Interesting(and fast feeling) movement mechanics, I really like playing games where I feel like I'm going fast and I really love the feeling of having advanced movement mechanics in a 3rd/1st person shooter. One of my standbys is Zdoom where I just fly through the levels and feel like a bladvass every time the double barrel shotgun reload lines up perfectly with an enemy.
A lack of mouse acceleration, I physically couldn't play Just cause 2 for years because there wasn't a solution for the horrible mouse acceleration in that game.
Not having enter be the ok button, Fallout 4 dodged this just barely by letting you press E for enter. But it is DISGUSTINGLY common to have games that require you to use WASD and then press ENTER of all keys to say advance text or press yes.
Rebindable keys, this isn't always a problem with me(unless crouch is the C button) but it is a massive issue for a friend I have who is left handed and can't really do a WASD setup.