You know you are reading fantasy because everybody is a suicidal lemming with no self-preservation instinct. In fact, you know you are reading modern fantasy because everybody (especially the bad guys) cares about his survival as much as the random pin-headed monsters that populate video games: “Oh, look, here’s that guy who has killed hundreds of [insert enemy] like me. Let’s attack him! I’m sure this time will be different!”
Knowing that the writer of a story is drawing most of his (probably unconscious) inspiration from movies or video games —worse, that he is not aware of that and believes he writes “realistically”— has been for a long time my #1 source of reading wrath and frustration. And there’s hardly a better place to see that in action than when characters are trying to murder each other, and since I’m talking about fantasy & adventure stories here, that seems to happen quite a lot.