Honestly, this is a tough question to answer. We've been tourists in Paris twice now, each time for a few days. We've had a rarefied experience: staying in nice hotels, visiting museums and gardens, shopping in boutiques and galleries, and eating in cafes and restaurants, most of which were recommended by others who have visited before. It's hardly what one could consider an immersion in the culture and my impressions are mostly snippets, so those are what I'll share.
Actually, for probably the best take on Les Parisiens, you should check out the Stuff Parisians Like blog, written by Olivier Magny, whom I missed meeting in New York by just about an hour...cursed prior plans! Funny aside: the driver who picked us up at the CDG airport when we arrived in Paris immediately launched into telling us about the fabulous Picasso exhibit at the Grand Palais.
(One more note: I know that any population is comprised of individuals, many of whom cannot fit into broad generalizations. I'm speaking from my own impressions and experiences, and do not mean to offend anyone whose experiences and view may differ.)
A sense of history and context. Here in the U.S., we tend to hold fast to the concept of unlimited possibility (even when it gets us in trouble, right Wall Street?), and tend to value the shiny and new over the well-worn and lived-in. Walk around Paris, and it's almost impossible not to be imbued with a sense of history, and I have to believe that growing up and living with that every day results in a different view of the world. It seems to me that Europeans have a much deeper sense of history, of their place in a broader community, of limits to expansion of power and accumulation of wealth, and of the fact that we're all sharing the same sandbox and need to play nice, or at least work out our squabbles. Europeans have lived many centuries with the understanding of limited resources, and are far less wasteful.
Education, kids and dogs. Walking through the Musée Cognacq-Jay (which houses among other things a fabulous collection of 18th century paintings), we turned into one gallery to find about 20 pre-schoolers sitting quietly in a circle listening to a teacher talk about the paintings. There were no cartoon characters, nothing flashing or playing music, and these kids were listening attentively. It makes me think that we tend to underestimate young kids' intelligence and attention spans, but regardless I've never seen anything like it here. At the Musée Jaquemart-André I watched as a boy who appeared to be about 7 or 8 years old listened intently to his audio guide as he regarded one of the 18th century portraits. Expectations seem to be higher for kids when it comes to behavior, and the same is true for dogs, who are allowed in restaurants and shops. Dogs sit quietly on a chair while their masters enjoy a meal or cup of coffee. Perhaps because they've been allowed everywhere, they don't run around trying to sniff (or pee on) each corner or post. (And now that there are fines, Parisians themselves have become better behaved about picking up the merde du chien!)
Materialism, clothing. As many have mentioned, quality trumps quantity in Paris. That doesn't mean everyone is strutting around in designer clothing, but most Parisian apartments don't even have closets (rather clothes are kept in armoires) no one is able to accumulate a lot at once. You also don't see much flashy jewelry (though the chunky rough stone and bead necklaces still seem to be popular) or bling-y clothing or handbags (exception: subtle metallic leathers). Refrigerators are small, so no Costco-size cartons of soft drinks.
Time. I had to remind mon mari that the waiter will not bring l'addition (the check) until you indicate you are ready for it. Even if you sit at a busy cafe with an empty coffee cup, no one will rush you. Working Parisians seem to take time for leisurely lunch, even enjoying a glass of wine, dessert and coffee. I don't know if most workers are paid hourly or are salaried, but no one seemed to be rushed or checking their watches. I've heard that this is changing, and that more Europeans are getting into our bad habits of eating lunch at their desks, or wolfing down food on the run.
Guilt, satisfaction vs. gratification. It's long been une femme's contention that Americans tend to be a guilt-ridden lot who don't allow themselves to fully experience satisfying, pleasurable experiences (and nowhere is this more true than when it comes to eating). Hence we've become gratification junkies. We deny ourselves good bread with butter and binge on crappy fast food. We tell ourselves that lovely cashmere cardigan is just too expensive and buy a bunch of cheap acrylic crap that itches and falls apart after a few washings. We want it NOW, we don't want to wait, when actually savoring the anticipation and finally getting just the right thing would be far more satisfying. A Sunday stroll through the park, an espresso sipped at a sunny sidewalk table, a bite-sized chocolate that is heaven on the tongue...the French seem to understand that little daily pleasures are necessities. (The movie Chocolat also makes this point quite succinctly.)