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.
I'm convinced that the ruler walked away, not because of his money, but because of his pride. He thought he was good enough. He was expecting an "atta boy" from Jesus and Jesus told him that he wasn't yet accomplished. The ruler needed to rely on Jesus' mercy rather than his own goodness.
The church has done a good job of teaching us to be "good" or not "bad" at least. We know not to cuss or drink or smoke or call people names or hate our neighbor and we are good at charity. God-fearing Christians are pretty good at emulating the rich young ruler. The church has done a lousy job of teaching us to be reliant on Grace alone. We are too busy being good sometimes.