I've already commented on your youtube video but I think you should not (primarily) try to sell it, the 3DGS user base is pretty low for that, but create your own game with it. If you add some enemies you are fine, just throw a few levels in there and you're done!

Btw. I've once (or multiple times) worked on a shooter myself but I could not get the shooting mechanics right. However, I implemented Superku style movement but as a FPS. You could run on walls (around corners, too), do double (and rocket) jumps, and so on, and to my surprise the movement in Titanfall looks identical to my old game. This may or may not give you some idea(s) for your own game.