I don't like the term "two faced" simply because being two-faced implies an intentional double image, in other words someone purposefully acts one way to mislead and deceive another for ulterior motives.

Do we all have faces and images we show in different instances? absolutely and this is called etiquette and privacy. There are certain things that you keep concealed for purposes of privacy depending on how close or trusting you are of the other person in the relationship. I think there is a big difference between this and being what you refer to as fake.

My simple answer is no, we are not all "fake" but we all do have certain amounts of information and self that we reveal in different environments, settings and groups. If I'm going to a group of people who are a bunch of gamers that I enjoy meeting with, I'm not going to go in there and reveal all my love life troubles and/or other personal issues that are not appropriate for that group. Would I be pretending by putting forth a face of someone that is doing alright or is that just the appropriate amount of information to share with that particular group?

being a completely open, and revealing everything about you and your life is just not a wise thing to do with everyone you know.

Be careful about how you frame this. we are different with different people for good reason and I would not look at it as a negative in many cases.