Is man born in God's image, or was that just Adam? I have noticed many Christians say 'we were born in God’s image', but the scripture seems to imply that men are 'born in the image of their Father, the Devil?' 

For example:


  This is how we know who the children of God are and who the children of the devil are: Anyone who does not do what is right is not a child of God; nor is anyone who does not love his brother. (1 John 3:10)


Which is it then, is man created in God’s image after the fall, or the Devils, or neither?
All of Humanity is (Individually) Made in God's Image

Genesis does not seem to leave the matter open to much interpretation.


  Genesis 1:26-27 NASB  Then God said, "Let Us make man in Our image, according to Our likeness; and let them rule over the fish of the sea and over the birds of the sky and over the cattle and over all the earth, and over every creeping thing that creeps on the earth." God created man in His own image, in the image of God He created him; male and female He created them.


Both Adam and Eve were made in his image, and by simple inference, it would seem to extend to all humanity. He later told them to be fruitful and multiply, then repeats the part about dominion, as if to say that their progeny would be like this.

One could perhaps argue that since the fall, man may be fundamentally different in the matter of being made in God's image. I do not think a straightforward reading of the text provides any real grounds for such a conclusion, though.


  Genesis 9:6 NASB  "Whoever sheds man's blood, By man his blood shall be shed, For in the image of God He made man."


This command to Noah after (sin, death, and) the flood I read to be an affirmation of an enduring unity between "humanity" and the "image of God" that not even the presence of sin can take away. It is as if the image of God is some sort of indelible mark on each human that cannot be marred or lost and whose value is not something we earn or lose. It is who we are. It is perhaps the thing about us that God finds valuable enough to redeem at awful cost.

The question didn't really include anything about the meaning of imaging God, so I won't attempt any discussion on that here, though it might be interesting.

The Image of Other Things

The second piece of the question mentioned being "born into the image of God or the Devil."

One definition of the word for "son" (υιος; 5207) is "used to describe one who depends on another or is his follower," and this is frequently used when biological sonship/fatherhood is not thought to be possible, "sons of the prophets," "son of hell," "son of the devil," "You are of your father the devil," etc. 

Nowhere is there any link made between being a "son of" someone and being born/made "in [his] image." We are all (still) made in God's image, even if we are "sons of the devil," because imaging God is a defining human characteristic and being a son of the devil is a description of our behavior.

EDIT: I forgot about Genesis 5:3, although I would consider that tangential to the point. The question has to do with being a "son of God" or "son of the Devil," and imaging that "father." When these phrases are used in the New Testament, they are referring to behavior. I would consider it dangerous to draw too strong a conclusion from Genesis 5:3 and Genesis 6:2. Seth resembles Adam, though not only in the ways that Adam (or any human) resembles God. The language of Genesis 6 is too "wonderful for me" to speak with certainty as to its precise meaning, but I don't think it's attempting to elucidate the concept of "imaging" in any way.