@slazenger hahaa I see what you did there
I have to be more precise. While 1 shot 1 kill might feel good, it also might not feel good. Why is that?
It basically comes down to the feeling of competence by the player.
Player will always give bigger value to kills that required more of whatever skill (aim, movement, positioning etc.) to achieve the kill. Player will feel more competent and the kill feels more satisfying and rewarding. On the opposing end, easy effortless kills will not feel as satisfying compared to the kills, that make the player feel that he is a skilled player.
That is why headshot in CS feel satisfying and rewarding for @Benz. This is also why for me, while INS2 has satisfying moments, there is also a lot of unsatisfying point-n-click kills that don't give the feeling of competence.
You are right, that if COD had OHK headshots, it would most likely be more fun for a lot of people. Does this mean that making every gun in Sandstorm OHK chest makes the game more rewarding/satisfying? Not automatically. It could be argued that chest shots require less skill than headshots just because of the size of the hit area, thus they would be less rewarding/satisfying in general. So that's why OHK doesn't automatically enhance the gameplay experience. This is also a very subjective thing. So we can come into the conclusion that "1 shot 1 kills feel good and are satisfying" is not really a fact.
Something else to add here:
Higher skill ceiling in game allows for much greater feeling of competence. I'm pretty sure that's why CS for example is so popular. People are enjoying the game, because it can really make them feel competent and skilled.
Now, before someone rushes the thread yelling "MUH SKILL BR0 GO PLAY CS I WANT SANDSTORM TO BE FUN, NOT SKILLZ!!1!": Feeling competent and skilled when playing the game IS fun And that's basically where the root of the argument for OHK TTK is, it makes some people feel more skilled in the game, thus makes the game more fun for them (at least for awhile), which I understand (but don't agree with!).
Skill and fun are not mutually exclusive, quite the opposite. And this is a fact and there's research about it.