This is all taken from the 'why don't more games have this?' thread. Just imagine all these things, but specifically when a game doesn't do them:
In Unreal Tournament, if you're crouching, you can't fall off a ledge. You physically just can't do it. It's so stupidly simple it's brilliant, and all 1st person games should have it.
In Goldeneye, higher difficulty adds more objectives to a level. In Perfect Dark it sometimes even changes start points and opens other areas you have to go through instead of the ones you know. It's hard to describe how much benefit this brings to replayability. All games set in enclosed pre-planned levels should have this.
Star Wars Battlefront II released in 2005 with a full singleplayer campaign, instant action against a full serverload of bots on every single level, and a 'choose your own path' galactic conquest mode that could be played solo, with, or against other people. All Star Wars Battlefront games should have this.
(And any Battlefield-like game, to be honest).
In fact, all shooters ever made should have instant action mode against decent AI bot opposition. Even singleplayer only shooters. This should be decreed by law.
Conker's Bad Fur Day allows you to skip cutscenes after you have viewed them once. More importantly, the start button will pause the cutscene just like it pauses any other part of the game. This system of cutscene management has never been topped and should become standard in all games with cutscenes.
Some games with long scrolling menus (I'm citing Perfect Dark again here but there are loads others) jump straight back to the top item if you press down when at the bottom. Again this is incredibly simple, but some games even today don't always get it right. Standardise it now.
In Prince of Persia: Sands of Time, when you first load it up, 'Start New game' is at the top of the menu screen, and highlighted by default. Once you have a save, 'Continue game' appears on the menu, but it is underneath Start New, with the latter still highlighted first. This is bad. All games with a front-end menu that includes a save-sensitive 'continue/load game' option should have it appear right at the top, and highlighted ready to go. We select 'continue' hundreds of times during a playthrough. We only select 'new' once. Also in-game pause screens should have the 'retry' option extremely close to the initial highlighted option. You want to absolutely minimise frustration time for players when they mess up in game. having to memorise a long winded menu navigation to restart is poor game design.