Considering how many different genres there are and what their different needs are, it's hard to think of any one thing that should be standard. I mean, Bejeweled does not need subtitles, for instance. But I can think of two things.
Accessibility Options
Colorblindness is not uncommon, so either an option to change HUD colors, or at the very least, redundant information that is not just expressed in shades of color is always good stuff. I remember FTL getting a colorblind mode and then some features from that bleeding into the standard view since they just made sense to do. Likewise, good subtitle options, with a nice big readable text, and closed captioning for sound effects available is also a very nice thing to have.
There's also the matter of input flexibility, if a game can be played with just a mouse or similar that's great, but it's also nice to have hotkeys for often used options. I'd applaud any game that actually uses Ctrl+S to save the game. Windows standard keyboard shortcuts are nice.
Universal PC Controller support
Not all games need controllers, and some are definitely not made for it, but if the controller shows up in the Game Controllers part of the Windows Control Panel and your game does NOT read it... you failed at controllers. Simple as that.