So when I played few levels of Quake (GL Quake, hires, 16bit colors), apart from seeing that the game is still very fresh and fun, there were few things I would really like to see in id games again:
- different ways to go through the level, swimming under water to get to different parts or simply jumping to neighbouring or lower floors, simply if you could jump or crawl there - you could go there
- various traps triggered by player being in line of fire (vertical from wall, horizontal from ceiling) or stepping on certain parts of the floor - the enemies also could get hit (and die) by traps missiles!
- enemies could start fight between themselfs if they accidentally hit each other (this was already in Doom), which considering low AI was very realistic feature and lot of fun to watch this random event
- at the end of each level, camera would show some level area from bird`s view and give the score, which is more old Doom/Quake style, but it gave you nice break from the first person POV
- another cool Quake idea was at the very beginning of the game - choosing difficulty and "world" you preferred to play by walking into a different teleports with different decorations, which made the whole Quake world look like layers and gave it more dimensions (also reference to various sci-fi/fantasy novels)
Especially with Rage, the game levels were very linear, restricting player to go through one pre-baked path. Then on the main "story level" there were side missions like Job Board and Racing, but this was not moving game anywhere forward and you had to go back to last story point X to continue to the next one.
Generally it feels like quite a few cool things that id themselfs invented, were forgotten or ditched maybe by influence from current trends, trying to be "more modern", who knows. It is definitely not easy if certaint product is sucessfull, to know what made it sucessfull, which things to throw away and what to add for the next title.