I prefer third person for one reason; First Person, while more immersive, CANNOT give you the level of awareness that you have in real life. You end up having to check everything visually. The better games have the red marks telling you "your attacker was in this direction" but what about simply brushing up against something?
A dimmer blue mark for non-pain awareness would be nice, and no; direct contact should not be required. The mark should get darker the closer you are to something, but you should be aware of it within a fair distance. Why? Your character caught it in the corner of his eye, or maybe brushed up against it, or can maybe hear it clearly, whatever. Maybe not for directly behind you, but 3rd person doesn't do that either; it just gives you a slightly more realistic eyesight coverage.
I know it's kind of a shallow complaint, but I feel clostrophobic in 1st person views, like a horse wearing that eye-visor thing preventing it from seeing to the sides. Take Mount & Blade for example, I dare you to master 1st person view! It looks fantastic and is immersible as hell, but actually fighting in that view? HA HA! No.