Rom 3:20 Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law [is] the knowledge of sin.
Rom 3:21 But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets;
Rom 3:22 Even the righteousness of God [which is] by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:
Rom 3:23 For all have sinned, and come short of the glory of God;
In your other post you mentioned other religions writings. It is your right to read and examine them and you should do that, then make up your own mind. I present what I believe and what you say you once did. This is to point out why I write what I write. I did not base my statement to you on the Koran.
As to your observation of the failures of human morality this is known, that is the reason Jesus the Christ was sent. It is unfortunate that those Christians around you are not all perfect, you will have difficulty finding a perfect human anywhere. But you will find many attempting to attain that state, Mother Teresa, Missionaries in Liberia and elsewhere, Christians in Pakistan, China, Indonesia, Somalia, etc. etc. etc.
Let me appear miraculously here and make a comment.
No one is above sin. Its part of our natures. People may claim to be Christian, or may just be bad Christians, but that doesn't mean that Christianity is the problem.
While scripture can be difficult to understand at times, there is meaning in it if you take the time, and trust in prayer. I think the Protestants threw the baby out with the bath water when they threw out a millenium and a half of well thought-out analysis of scripture.
And no, there isn't the kind of observational evidence like there is in a naturalistic approach, but let me say this;
What other faith, creed or philosophy has produced a free-er, more prosperous, more powerful nation, than the United States of America?