Facebook has changed everyone's email address from their profile to a @facebook.com email address without asking. Here is how to get your old email address back on your profile.
Click "About" on your profile and scroll down to your email address. Click "Edit".Click on the circle next to your Facebook email address and change its setting to "Hidden From Timeline".Click on the circle next to your other email address and change its setting to "Show On Timeline".Click the Save button.
That was it. Of course you can completely hide the email address from your profile.
Although you are given control to which email address is shown in your profile it's not a fare move from Facebook to modify your default email address without any notification.