When I played GTA 4 on the Xbox 360, I was divided. I enjoyed the game (apart from the heaving masses who poo-pooed it straight out of the box), enjoyed the story arc, and got my money’s worth out of it.
But there was something wrong. The amount of detail and processing that the game demanded did take its toll on the controls, but the whole experience felt sluggish and delayed, as if I were playing it inebriated. (Yes, I was actually sober when playing it.)
Turns out that there are several factors to input lag, and that making a game run like Call of Duty doesn’t just happen overnight. Mick West wrote a couple of excellent articles on the issue – one is a concise, slightly-technical yet easy to read article on what input lag is, why it happens and what developers should look out for. The second applies some common sense and describes a method of measuring input lag in a game using a digital camera and a CRT TV. Richard Leadbetter has some more commentary on this issue (registration required).
West recommends that games reviewers should also test for input lag in their games when doing their analysis. I, uh, will probably not be doing that.