All humans are now sinners. It's even a sin to deny being a sinner:
"1:8 If we say that we have no sin, we deceive ourselves, and the truth is not in us. 1:9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. 1:10 If we say that we have not sinned, we make him a liar, and his word is not in us." (1 John 1:8-10 KJV)
But it wasn't that way at the beginning. Humans were created sinless. Adam and Eve were sinless until they chose to sin, thereby causing the "fall of man." They, and all humans ever since, with the sole exception of Jesus Christ, were sinners. Only Adam, Eve and Jesus Christ have been sinless; Adam and Eve for a while, Jesus Christ for ever.
"God created man in His own image, in the image of God created He him; male and female created He them"
The creation of man (from the Hebrew word pronounced aw-dawm, meaning man as a species, male and female, even though the name Adam originated from the word for the species as a whole) was intended for them to be sinless, like God i.e. "in our image, after our likeness" refers more to character than appearance.
"1:26 And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.
Adam and Eve were observers of the only true Sabbath Day, the Seventh Day, just as the LORD Himself observed it i.e. violating the Sabbath is a sin, so Adam and Eve observed it because they were at first sinless. The Sabbath did not begin at Sinai; it began at Creation.
"2:1 Thus the heavens and the earth were finished, and all the host of them. 2:2 And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made. 2:3 And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made." (Genesis 2:1-3 KJV)
Genesis chapter 2 is a more detailed reiteration of the creation of man as described in chapter Genesis 1.
"2:4 These are the generations of the heavens and of the earth when they were created, in the day that the LORD God made the earth and the heavens, 2:5 And every plant of the field before it was in the earth, and every herb of the field before it grew: for the LORD God had not caused it to rain upon the earth, and there was not a man to till the ground. 2:6 But there went up a mist from the earth, and watered the whole face of the ground. 2:7 And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.
The (male) man was at first alone, just as God once was (God is called the Father because He had a Son). But from one man, another was created. Ironically, while Eve would become the mother of all humans, Eve herself was the only human to have been born without a mother.
"2:15 And the LORD God took the man, and put him into the garden of Eden to dress it and to keep it. 2:16 And the LORD God commanded the man, saying, Of every tree of the garden thou mayest freely eat: 2:17 But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.
Fact Finder: Adam, Eve and Jesus Christ were born sinless. All were tested and tempted by Satan to sin. Adam and Eve failed the test, while Jesus Christ always successfully resisted the Devil. But was it possible for Christ to have sinned? Why did Satan attempt to get Christ to sin?