But that still wasn't "good". "Good" is a worldy measurement which means nothing in Heaven. The "good" people will burn in Hell just as the "bad" people will walk the streets of gold. The rich young ruler was "good" in the eyes of the world. If we saw the ruler today, we would call him a "good Godly man".
Peter is a classic example. Peter was a screwup but Jesus looked past that. Peter needed Jesus because he was "bad". The ruler was "good" therefore he didn't need Jesus.
There is no good and bad in Christianity. There is obedience and disobedience.
Jesus said to him, "If you would be perfect, go and sell all that you have and follow me."
The goal isn't good by earthly standards, the goal is perfection.
There are only two ways to be perfect. Never sin or be forgiven. And God said there are none righteous so the first one don't count.
You are correct that in worldly terms, we have our own difination of what "good" is. For some, it is a "Good" morning, for others, it is not. For some, milk is "Good" for them, but if you a are lactose intolerant, milk is not "Good"
When Speaking in Terms of God (Father, Son, Holy Ghost), we have to take God ofr what it truly means:
Holy
HO'LY, a.
1. Properly, whole, entire or perfect, in a moral sense. Hence, pure in heart, temper or dispositions; free from sin and sinful affections. Applied to the Supreme Being, holy signifies perfectly pure, immaculate and complete in moral character; and man is more or less holy, as his heart is more or less sanctified, or purified from evil dispositions. We call a man holy,when his heart is conformed in some degree to the image of God, and his life is regulated by the divine precepts. Hence, holy is used as nearly synonymous with good, pious, godly.
Websters 1828 Dictionary
God is Good as God is HOLY. I agree that peter was a "screw-up", but he was a screw attached to the right Bolt. He know he needed Jesus. He know that others needed Jesus. The ruler was not good, as he did not recognise his need for a saviour. To him, it was as you discribe, obedience or disobedience. The things is, we can not live up to Gods standard, and the "good" ruler failed to see that. He failed to understand that while he had kept the civil laws (the last 6 commandments), the "good" ruler was placing his wealth above God. He was guilty of transgressing the first four commandments.