3D positional sound is a buzzword right now, and while it's cool and does adds to immersion, it isn't as vital as you might have been led to believe. Gameplay is a number of things, the way the controls work with your character onscreen, the way your character interacts with the environment, and the way this interaction makes the living breathing person behind the monitor feel. These feelings can range anywhere from pleasure or satisfaction to frustration and anger. A really good game will make you sympathize with your character. A game with poor gameplay is relegated to the bargain bin a few short months after its release.
Controls play a very important part in good gameplay.
Without good controls, it is almost impossible for a game to succeed. First person shooters are the example here. Any computer made in the past 6 years has a mouse and keyboard. This means they have all the special hardware they need to get started playing FPSes. This explains the popularity of Doom's shareware, it didn't need fancy joysticks, or even sound.