Since this thread was bumped anyway, I just thought I'd share some info about getting a game on Steam.
If you don't have a publisher pushing your game, one thing Steam/Valve will use to assess your game is MetaCritic. If you can get at least 4 reviews (enough for a MetaCritic score) and an average score of over 60, then your game stands a good chance of getting accepted on Steam. This was from a contact at a publisher who was able to get info from Steam/Valve after a game I worked on wasn't accepted on Steam after 3 applications - we had no other feedback up until that point.
You can check for reviewers used by MetaCritic here -> https://metacritic.custhelp.com/app/answers/detail/a_id/1508/ - this will let you prioritise who you submit your game to for review. Just go to the website of the reviewers, find their Contact page and look for an email address or form you can use to submit your game.
For example, if you developed a game and you released it as a mobile app, you could contact these app focused reviewers to up your metacritic score before applying to Steam (after you used an exe wrapper, of course).
All submissions should be sent to firstname.lastname@example.org
For PR, editorial, to organise reviews or submit assets for games please contact Paul Byron via email (paul[at]appgamer[dot]net) and Chris Thompson at (christh[at]appgamer[dot]net)
Submission form at http://www.appsmile.com/contact-appsmile/