Interface, interface, interface.
If I can't remap my keys, invert the mouse, or quickly identify what the on-screen GUI elements do I quit the game almost immediately.
This is why I could never stand the Gothic series. I spent 3 different occasions over the years doing everything in my power to like Gothic I. The interface is so horrific, that after two hours of diligently trying to 'adapt' to the game, I just couldn't do it. This is also why I've never been able to get past the 1st stage of System Shock I, terrible interface. This problem isn't necessarily exclusive to old games either. You can play The Bard's Tale or Wasteland, games written almost 30 years ago, and they still have very clean easy to navigate interfaces. The first and most important consideration of a game is the interface. This is why the latest trend of console bastardized cRPGs suck so hugely, because the interface is tacked on as an afterthought, or worse, the game itself was designed around the console controller. :huge sad face:
Edit: As others have mentioned, interface includes camera problems (DIAF NWN!), motions sickness inducing headbobbing (what idiot thought this up?), and poorly implemented FOV(console ports especially). Horrible stuff.
10. Tedious or Slow Travel
Lack of travel scaling on huge maps is unbearable.
A game needs to have some kind of fast movement scaling (Skyrim: Foot, Horse, Fast Travel). This is why I can't play games like Darklands. While Darlkands is an interesting game, I couldn't handle the unbearably slow movement and lack of ability to speed it up. Especially in dungeons. I don't care what the mechanic is, haste, levitation, or flying (Might & Magic), there needs to be fast travel scaling as the size of the map increases. I have quit many so-called 'great' games over this issue alone. As a footnote, runspeed is almost always the first mod/powerup I choose in first person RPGs like Deus Ex etc. for this very reason. Any first person RPG that requires a lot of back tracking and slow running (I'm looking at you Deus Ex : HR) is unbearable to me these days.