Isn't this a quote from Jerry Macguire? When Tom Cruise walks in and starts making a speech and Bridget Jones (Sorry, can't remember her name) says you had me at hello, which was the beginning of his speech?
The phrase also crops up in the animated film 'Shark Tale' said by the hero fish (voiced by Will Smith) - it's a sort of in-joke which refers to the fact that his love interest in the film is voiced by Rene Zellweger who said it in Jerry McGuire