there are videos on youtube showing hes face

It's better. The whole purpose of master chief is to allow the player to project themselves into that character. Master Chief doesn't talk very much for a reason. It allows the player to feel more immersed in the world as they effectively take the role of master chief.

I just don't think anything good can come out of unmasking him.

No it's better to keep him mysterious.

http://www.youtube.com/watch?v=3mkiRQVkERg

if he looked like that that would be epic lulz

they describe him in the books

it would be funny if it was really a nerd underneath with a voice changing mic.

I think it is better. I have my own preconception of Master Chief's face. Unmasking him, so to speak, would ruin that for me.

Its part of the great mystery!!  Master Cheif just wouldn't be the same if we knew what he looked like.

I wish I could find the funny video of him taking his helmet off, but alas it was nowhere to be found!