It means to be the role model of what a man should be like. Have a look at this entry on Urban Dictionary for a better idea.
There are several definitions there, i am kind of looking for what the men here think.
Why did you recommend Urban Dictionary?
Why not? The entry seemed to encapsulate the concept at hand.
Because the terms "man's man" didn't appear in my regular dictionary. The Urban Dictionary is a really good source of descriptions for colloquial language. You have to filter out some rubbish sometimes but that isn't an issue. I teach (Business) English to foreign learners and they find it a very helpful source, as do Europeans who move to the UK to study and start to encounter a very different English from the one they learnt in the classroom back home.
I think you're original statement sums it up nicely.
It means that to other men, you are what embodies manhood.
I think it's a great compliment, especially for the types of men who are drawn to this site.
To my understanding, "a man's man" is a guy that other men feel comfortable with, whom they trust, and who naturally embodies manly qualities.
Liam's link reinforces my opinion; it's different for everyone, just as the definition of what is manly.
To me personally it's a combination of male charisma, character and leadership.
Someone who almost universally attracts other men of all types, is not only comfortable with them but with himself. They lead either directly with moxie or indirectly through a strong example they set.
Someone put it to me this way years ago, and the words still ring true:
one who exudes a masculine sensuality that brings Life to everyone he encounters
No surprise someone has called you that, Stein. You are one.
Someone a man is likely to admire and want to talk to, I'd imagine.