2 months ago, a start up building a video game asked me for help on building a pitch to get accepted on a biz incubator.
They started by presenting me, as if I was the committee their pitch.
They clearly explained the biz model, their strategy and the segment they were aiming for, but they did not show anything about their game.
It was fine but was not attractive enough.
The fun component was missing.
They did had a sort of prototype which was light years from been functional.
however we aid them to create a cool video which was self explanatory.
This video showed the game mechanic and added the fun factor to the pitch.
So, dont build an entire prototype, build the minimum functionality to validate the mechanic and ensure is FUN. then spend some effort on building nice graphics and create a couple videos, add those to your pitch.
If your game concept is fun, you just have to prove you are the right person to make the project happen.