Pitching a movie idea

In class we were asked to think of a film and pitch it to our teacher and the class. We would then receive feedback from it and discuss if it was a good concept or not, what could change and how we could improve. My idea was of a slasher-thriller called stalk, the plot would be boy meets girl, boy falls in love, girl hardly notices him, boy kills off competition and tries to get close to her. The idea that we already know the killer was brought up, so I suggested there's at least three suspects all making friends with her at the same time, leaving suspicions high. I linked the story to the ending of Sorority  Row, where a all girl Sorority were being hunted and killed by the boyfriend of the main character. I placed my target audience as 18+ men and women which seems about right for a horror/thriller. We also heard other pitches such as a action take on a film like Catch Me If You Can type film, where the criminals are escaping from the law. A drama based on a homeless man, living on the streets and we see the lives they lead through their eyes. When comparing these ideas with others we all agreed that, though mine was good, both those ideas surpassed mine. Therefore I am putting that story into the back of mind, in case we want to go back to it, and looking at other ideas which I can discuss with in the group. Perhaps a film like Kidulthood, showing the life of teenagers and gang warfare.