Work flow rules

I am trying to set up a workflow rule that would alert a user if someone else creates a case for them. It would be nice to make the rule that says to send an alert when the case owner is not the person who created the case.

Right now the only way I see to accomplish this alert is to make an alert for "User1" executed on creation with a rule that says "Case Owner is User1" and "Created by isn't User1". But then I have to make a new rule for every user. I have more than 10 users and only get 10 rules.

What am I doing wrong?