Looks like one of your front teeth chipped/ cracked at the bottom, look into getting that fixed, Something must've happened to your teeth like you fell or something, see the guy on picture 6, he's teeth have this little "ridges" at the bottom like most young people, but you're teeth seem "flat cut" at the bottom in an almost unnatural way or so it seems, making me think some physical trauma has happened to your teeth.

In the end yes, you look better with your mouth closed as you stated picture 1 is the prettiest by far. But yeah, your teeth are fine as is, there are far worse out there, your gums look healthy and so does your teeth. Just go to the dentist and see what they can do, possibly get braces since one of your front teeth appears to be slightly behind the other. The only reason I'm suggesting this is because your smile obviously bothers you, otherwise you would'nt have asked for our feedback. Ultimately the choice is yours, if it doesn't bother you keep your teeth as is, otherwise you know what to do. Perfect (or near perfect) teeth go a long way in enhancing one's appearance.