#3 has the greatest emotion! #4 has it too, so adorable!
Now onto aesthetics and technicalities...
#1: The background isn't too favorable, try and go with plain background that won't distract the eyes and take away from the subject. The photo is a bit dark, maybe dodge the whites a bit and the whites of the eyes. Also, you want those eyes to pop more. The yellow shade by the muzzle and body's far left is distracting too, try cloning it out.
#2: Same background issue. I think it could do with a hair of brightness. They eyes are like two black beads, no division between the pupil and iris, or is that how their eyes are? It doesn't bother me much, it's up to you whether you want to edit that.
#3: EPIC! I love it. Minor flaws include the cutting off of the right paw, amputating the left, shadows on the left and the background on the right. I think the dog's coat is a bit too saturated, maybe bring it down a tiny bit? But you
definitely nailed the emotion and that's great when you do so with an animal (aka kid!
)
#4: A bit too dark, I like the light that catches in his/her eye and I love the thoughtful look <3