okay...no laughing, I just saw this on one of the court TV shows. The ring is an invitation for marriage, since you did not get married, the ring should be returned to him if he paid for it. If you both made payments on it, then you have a completely different story.
Another scenario is if the ring was a gift to you for your birthday or Christmas etc., then the ring is a gift and it is yours.
In any event, I am no where near an attorney, just enjoy watching court TV shows and see many different cases. You could just wait to see if he really takes you to court over it.