Oh this is fun!
1st rider-His back is slouched, big nono, chin is down. His legs drive me CRAZY!

hid foot is not in line with his heel, he basically looks like crap. His elbows aren't bent, and one thing nobody else noticed, but look at his hands. They are wide open! He needs to learn how to use his body, this pic makes me sick.
2nd rider-For HUS, this girl has a good start, just needs some finishing touches. I think her leg is good, although her foot is too far back. She needs to stretch her body upright, as she is a bit slouched and is ahead of her horses motions. A little more bend in the elbow would help. On the positive side, she has a strong calf, her chin is up, and her hand is closed.
3rd rider-Well, she needs a lot more weigth in the heel, and I prefer more closed hands. However, she is my favorite as she is on her plumline and her back is arched beautifully, chin is up, and her elbow is bent.
1st horse-YIKES!

The first thing I noticed was the horses headset. A good headset is poll lined up with withers. His nose is way too far out, possibably because the pit is way to high in his mouth. I HATE seeing a huntseat rider not keeping contact on the bit and getting their horse collected. I feel sorry for this horse, because all his faults are from his training. He looks to be a beautiful mover, but the glimmer in his eye is gone, he almost looks scared.
2nd horse-His head is a bit too low, but his nose is where it should be. He looks to be moving nicely, and there is a good connection with the bit. This is my favorite of the three.
3rd horse-This is the only horse with his poll in the correct place, however his nose is a bit far out. Once again, no connection on the bit, icky. If you look closely, this horse in underweight. He has NO stomach, and his hips are slightly protruding. He also looks long backed, one of my pet peeves. However, he looks like he is enjoying his job, which I like to see.
I would agree with JustDressage it on the placings.