I don't see why people like so-called realistic video games. For example, people often say Call of Duty: Modern Warfare 2 is realistic. I don't see how a game where you can heal in 5 seconds and get killed by a knife to the foot but not from a .50 cal bullet to the stomach.
Yes, a game must have some realism. I wouldn't play a game with Big Rigs physics, but I have never heard any reviewer even use the word "realistic." Ever.
If you think about it, Halo 3 is more realistic than Call of Duty: Modern Warfare 2. Why do you have a HUD in MW2? Who knows? Why does your health recharge? ...superpowers? These things can at least be explained in Halo. Both are great games, but I don't feel that realism adds much if any value to a game.