O hum~  quickie edit:
Circular emotes are my specialty, but I'll try my best.
First one's mouth needs more curve, and I decided to try a different approach to the eye.  Second one is pretty good, I added some AA on the inside of mouth and took a different grin approach too.  Third one's eyes need some AA, I've put two different ones there :P
Can't get to  editing angel and devil sorry, but I can give some crits.
Angel's expression is flat and somewhat a blank smile.  Try to give the eye some shine or character.  And maybe the grin bigger.  Halo should be wider too.  Devil ok, but horns need to face opposite directions.