I've been going to all three of these stores for the last year or so. I've seen them all go through some not-so-impressive phases. I've been in animal city and saw plenty of healthy fish (and other animals), but I have also went in and seen lots of dead fish, and lizards with burnt misshapen noses from getting to close to their heat lamps. I dont go there much.
Wet pets seems to have pretty healthy fish and a great selection of supplies. Be careful about the neons though, I was just in there and saw white patches on the bodies of a few neons, Could be ntd, could be something far less serious. I would prefer not to risk it.
I think AW is my favorite. The variety is always impressive and I feel like I see something new every time I go in there. On average the fish I buy from AW and AC both seem to have pretty good survival rates, though I've had my lemons from both.