Why is "being created" considered an imperfection? I've seen the uncreated God contrasted many times to the created angels, Satan, and humans, and etc. Being created is counted against the latter category as a mark of imperfection which God does not bear. 

However I don't really see why being created is an imperfection.  Surely something can be created and be created perfectly, right?  To become perfect?

Is there a way to understand this through the bigger picture of what perfection is?  Or is this something that must be understood on its own?
Being created doesn't affect perfection as much as impassability. The doctrine of impassability states that God cannot change- that he is the same yesterday, today, and tomorrow. If God (or Jesus) were created then he has changed - he went from not existing to existing. 

The tie in between perfection and impassability is this: if God changes, then it sets up a situation where God is not perfect. If he changed, he would, it is assumed, move to being 'perfect' from a state that was necessarily 'less than perfect.' That previous state, adherents of impassability maintain, is inconsistent with the nature of God's perfection, hence it cannot be.