Actually, the recipe is really simple
Make a game which someone would like to play it more than once, or/and make him smile, or challenging him in a way.
Awesome Unique Game, might be hard to determine, Awesome game, yea, but what is an awesome game? 
Unique Game? Not really. Making Unique game does Not guarantee you that it will be a hit. I haven’t seen any Zombie Motorbike driver whose tires are about to explode as he drives pass humans, but when I think about it, is that a something I’d like to play? I hope you understand me 
Thoughts:
Back on the start on my point. If you make a good game which has replay valuable, or/and brings some sort of emotions on people (happy, sad, scared, excitement, etc…) You are one step closer of making a popular game.
Then, spreading that game to web portals/studios where there is enough traffic, its highly likely that many people will play it, and if they like it, start distribute it on their own, the game or the game brand (video). This is how the Flash Games were working good for the past 10 years, on self distribution and self promotion.
However, with the loads of spammy, clones, decent and great games out there, your chances are really low. As suggested above, do contact people for reviews (although all Youtubers are busy and “demanding” of highquality nowadys), write in forums, showcase your games whenever you can, redit, facebook, etc, and back on the first thing, if the game is good, it will continue its distribution.
I myself have bought loads of games, and while high-polished popular genres (multiplayer, or/and strategy, RPG, etc…) games of xx,xxx budget can’t spread on their own, its more common to see low-budgeted games going in viral madness.
Good luck!