You are right in a certain context... this isn't it.
You are talking about quarterbacks who stare down their primary receiver from snap to throw and never look elsewhere. No, successful QBs do not do this. I'm talking about purposefully looking to another receiver with the intent of convincing a defense that the ball's going that way, only to turn off and hit a different receiver with little to no warning. This is what the vision cone simulates, and this is what I'm talking about.
Every quarterback worthy of being in the NFL understands that you cannot stare at a receiver you intend to throw too. These quarterbacks cycle through receivers (in a passing-lane scheme, such as Dennis Green's offense) or their reads (in a defensive key scheme, such as Mike Holmgren's offense) before looking to the intended receiver.
However, someone like a Montana, Brady, Manning, Young, Marino, can make their reads very quickly and can purposefully look to a secondary receiver and watch him, hopefully drawing the defense to that spot, then, almost without a glance, can turn to their primary and make an on target throw.
These throws are just this side of blind, and if Kyle Orton or Tarvaris Jackson tried it, would produce more interceptions than completions.
To produce the effect that the vision cone does, a QB must have two things: an outstanding ability to read defenses extremely quickly and a knowledge of his own offense not even his head coach can match. Even the very best cannot do this on every play (well, except maybe Montana).
Madden without the vision cone produces a similar effect to 9 out of 10 plays: The defense does not look for and does not react to the QB staring, and the QB simply cycles through reads before he makes a decision and makes no attempt to "draw" the defense anywhere. He doesn't stare down any one receiver either. (It's especially apparent when you consider that someone like Ed Reed knows damn well not to believe Payton Manning's eyes).
Everything I've said here is a bit of a simplication of the whole thing. There are so many factors that go into it... someone like Manning or Brady can, indeed, stare down a receiver at times because just because you know who the ball's going to doesn't mean you know when or where it's going to go to him, and there is no defense for a perfectly timed and placed pass... that's why the front seven is more important to pass defense than the secondary. The secondary can do everything perfect, but if the QB makes a perfect throw, the offense wins.