I feel for you man... I'm German so I was able to read some of your blog a while ago, and saw how high the stakes were for you and how much you suffered for your game. I've somewhat been in the same situation, with lower stakes and much less time invested, but a lot of effort and dreams were crushed by reality.
I now take things slower, work a part time job in a kitchen (that I enjoy and where I don't have to sit), and focus a lot more on learning and improving rather than putting all my energy into one game and hope that it will be successful. The last game I published I knew it would fail, but I tested some stuff out and got better.
My advice would be if you love making games so much, live your life and create games on the side, use free software and publish in places where it's free to publish, like Kongregate and Newgrounds. And get as much feedback as you can, because to be honest there would be quite a few things I'd criticize about your last game.
About knowing what makes a game a success, there are at least a dozen podcasts about game development, some very good articles on gamasutra, and speeches on the GDC youtube channel, definitely worth it to listen to it here and there and soak it in. Sure there are games that are crap and are very successful, but that is the exception to the rule. I'm pretty sure that by knowing the quality of the game and the marketing effort (and it's quality), a pretty good prediction of the success can be made.
I whish you all the best, would be nice to one day hear from you again with good news!