@sirius
Ah, this old falsehood.
Alright. The most immersive game ever sold is Dead Space. The reason is that all UI elements is presented within the game world instead of 2D elements that does wonders in reminding your brain that the 3D depths is just an illusion. 3rd person allows for so many thing that support immersion, that the detriment of looking at your avatars back is hardly worth it.
What is more, if you tilt your head to the side, baro-receptors remind your brain what direction up is. This does not come in effect in first person. Then you have all these camera jolting that tries to sell the “immersion”. Since you have NO other senses to guide you, it is pretty much analogous to sitting in a washingmachine.
Finally, 3rd person allows for interaction with the game world, which sells the reality of the world to the player.
No, First person is NOT defined by immersion. All it does better than 3rd person is IMMEDIACY. Nothing else. This first-person immersion is a false narrative that just wont die.