well, you aren't actually competing against all 4000 of those steam games released in a year, you are competing just against the ones in your subgenre, other shmups. if i were you, what i'd do is go through this list of all shmups on steam:
http://store.steampowered.com/tag/en/Shmup/#p=0&tab=NewReleasesthere are 399 shmups on steam. so that's still a large, but much more manageable, thing to consider.
play as many of them as you can afford, and learn from each. look at each one critically, find where it shines and where it fails, and adapt your game to that market so that you don't make similar mistakes and you do some of the things that worked for other games in that genre.
i'm not talking cloning, but rather a higher level learning process. if you find a shmup that succeeded because of x, y, and z factors (in the abstract sense), intelligently try to apply those factors to your game as well. this can include gameplay, graphics, the way the trailer works, or even just how they marketed themselves.
pay particular attention to other shmups that have a neon look (such as, for example, the geometry wars games). because that's a sub-sub genre, those are the games people are going to be comparing your game to. visually, your game does not look as good as geometry wars, an indie game that was released 10 years ago. so that might be something to work at.
i think i posted earlier in this thread something along these lines (regarding learning from competitors), but i want to post an article i wrote on marketing here in the hopes that it'd be helpful:
http://rinkuhero.tumblr.com/post/157442122632/indie-game-marketing-advicei know it might sound silly to say that playing other games in your genre is 'marketing', but it really is -- even just spending a few hours a week playing other shmup games on steam (a new one each time) would help you enormously.