The best elevator pitch doesn't pitch your project. It pitches the meeting about your project. The best elevator pitch is true, stunning, brief and it leaves the listener eager (no, desperate) to hear the rest of it. It's not a practiced, polished turd of prose that pleases everyone on the board and your marketing team, it's a little fractal of the entire story, something real.
It's not about what you've done. It's about what you are going to do and who you are going to surround yourself with while doing it.