I have been to Paris.
When I was there, apparently every other store on the block was selling, essentially, ham and cheese sandwiches on a baguette. "Jambon et fromage". They had cases stacked with them.
Simply, they were amazing. I wasn't there long, but I ate several of them. In fact, the last meal I had at the airport was one of these sandwiches and it was amazing as well.
I can't put my finger on it, was it the ham, the cheese, the bread, "being in Paris", but it's been difficult to find anything comparable here. Our "sub" sandwiches are just not the same as these things. Even the sandwiches at, ostensibly, "french" bistros aren't the same.
Maybe it's the water.
But, anyway, I know what I'll be eating as soon as I return, whenever that may be.