All married people? Really? You must know some very miserable couples.

But this isn't really a question you can ask in this way. It's better to be single if you haven't met someone you want to marry. If you have, well, it's nice to be married, though not essential.

I love being married. To me, it's infinitely better than being single, because I married the right person. So no, not all married people think that. But you're talking about marriage like it's some kind of independent activity and not a step on a path you follow with someone else.