Your question landed in two categories centered on Jewish thought and practice,
so here's the answer from a Jewish perspective:
The so-called "Ten Commandments" are ten out of a total of 613 commandments
that Judaism recognizes in the Torah, that Jews are responsible and accountable for.
The attitude of Judaism is that there's no way that we can know or understand how
to prioritize them. We have no idea of which ones are more important and which ones
are less important. There's no way for anybody to take the list in terms of importance,
draw a line across it somewhere, and say "I'll keep the commandments down to here,
but the rest are for people who are more religious than I am."
We have commandments to honor our parents, pay our employees on time, avoid
eating non-kosher food, help the guy whose donkey sank to its knees when the
load got too heavy for it, observe the sabbath, teach our children, give our dogs
the meat that we can't eat, avoid murdering and stealing, and send the mother
bird away before we take eggs from the nest. And nobody knows which one of
these is more important than any of the others.
The first and most important statement is that HaShem is one and there are no other gods. This is reinforced by the daily recitation of the Shema by Jews.
Another of the Statements that is always mistranslated by non-Jews is the prohibition against murder. This Statement is mistranslated as the prohibition against killing.
Let's just stop and think for a minute: There's no priority or ranking listed alongside the "Ten Words" ... neither the first time they're given in The Bible nor the second time ... so any answer to that question would have to be a matter of opinion, which might well differ from one individual to the next. But that whole game would be a process of human evaluation and prioritization of divinely revealed material, which would kind of defeat the whole concept, don't you think ?
What I'm suggesting... and you're certainly free to disagree ... is that all Ten are tied for First.
Christian Answer According to Matthew chapter 22, verses 35 through 40, a lawyer asked Jesus, "Teacher, which is the great commandment in the Law?" Jesus said, "'You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.' This is the great and foremost commandment. And the second is like it, 'You shall love your neighbor as yourself.' On these two commandments depend the whole Law and the Prophets."These two commandments do, indeed, "sum up" the other commandments; for example if you loved your neighbor as yourself, you would not kill him, steal from him, or lie about him.
Catholic Answer:
The most important commandment for Christians is that you should love the God entirely, and your neighbor (ever single human being in front of you) as yourself, from the Douay-Rheims translation Saint Matthew, Chapter XXII, verses 35-40:
And one of them, a doctor of the law, asking him, tempting him: Master, which is the greatest commandment in the law? Jesus said to him:
Thou shalt love the Lord thy God with thy whole heart, and with thy whole soul, and with thy whole mind. This is the greatest and the first commandment. And the second is like to this: Thou shalt love thy neighbour as thyself.
On these two commandments dependeth the whole law and the prophets.
The first of the Ten Commandments is the most important. It states the existence of God. Once one believes in God, other commandments (honoring one's parents, not murdering, etc) become axiomatic. See also:
I think that the most important commandment is the one that you have the most struggle on.
Honor thy Father and Mother.
"Thou shalt not kill."
the ten commandment are so important because they will get you to a better place and that is with the Lord as an angel forever
The Torah teaches us that they were the first commandments given to the People from God.
the ten commandments was for the people who believed in god.
The commandment forbidding adultery
The ten commandments is not a code of law.
A:The first four of the Ten Commandments were written to command obedience to the Jewish religion, and the remaining commandments were concerned with social harmony. The fifth commandment tells us to honour our parents, which is a commandment about family relations. This was deemed so important that the Bible says that if a son strikes his father, he must be killed.
the Ten Commandments.
In the old testament the ten commandment was kept in the ark of the covenant and the priests carried it.
I'm pretty sure it was the eighth of the Ten Commandments.
The ten commandments were given to Moses on mount Sinai. The commandments had been written by the hand of God on two tablets of stone.
The second of the Ten Commandments is not to worship anything other than God.
The ten commandments are important in religions as they are rules to live by that have been set by God.