What would you consider one of the top 3 things that makes Vietnam different from other countries?  

I agree with everything you said. They have their own culture, rich with traditions. I have never been to another place with such welcoming and friendly people either. Japan has friendly people but they are not social. They like to mind their own business. 

The people stand out the most to me. They will go out of their way to be helpful and kind, especially to complete strangers and people not from their home. It always amazes me and fills me with hope for the future that people are capable of being beautiful and kind human beings. 

Their traditions and holidays stand out to me. I would have said the same as you OP but I wanted to add a bit onto it. I think they have amazing traditions and beautiful holidays all their own that set them apart. 

The price of everything. You get so much for your money be it food, hotel stay, gifts, whatever! I have never been to a place where my money goes this far. I am able to do so much on a tight budget. 

What you have written is true, but  ld add a very important thing : I have never seen such a small country (331000 km²) with such a diversified relief; apart from deserts, you have everything from plains to limestone peaks, swamps and jungle, and others. And Halong Bay is unique in the world !

The architecture has its own charm that sets it apart but you have to look at the finer details to notice it.  Outside of this, the people is up there for sure. So many friendly people live in Vietnam. It is hard to believe they have an sort of crime.