See Romans 6:6 and Colossians 2:11 (in the kjv preferably; but the NLT is also good).
Also, compare 1 John 1:5 and 1 John 3:5 to 1 John 5:20, 1 Corinthians 1:2, 1 Corinthians 1:30, and 1 Peter 5:14.
There's no comparing to be done on this. John is not telling us "we don't sin" He is telling us not to "practice sin."
Sin is not just in the actual actions of doing, sin is also in the thought pattern of fallen man.
Have you ever seen a drop dead gorgeous woman walking wherever in her heels, with her blouse busted open and skirt up to her butt?
Jesus said if you lust after her in your mind, you have sinned. Just for a split second you have that impure thought because of her beauty, you have sinned the same sin as actually having sex with her, which is fornication.
Have you ever been angry with someone and found later that you were wrong in your anger, well, according to Jesus you have sinned.
It goes on and on, Jesus has shown us what fallen man really is. He has shown us that our righteousness is impossible in any form. We are at the mercy of God, but thank God He has mercy on us and provides us with that perfect righteousness through Christ.