Have you GM'd any roleplaying games before? I think that's great practice for thinking about this particular design problem. Or even just finding a forum or blog on the topic and reading what people love and hate in a GM. Since the game is being run by a human, you do get to tailor the world to your players. With something like this you can try to capture some of that flexibility a human brings to the role of running a game.
You mention favorite stat and giving a bonus to it: Advice I've taken to heart in GM'ing is to try to give everyone a chance to use a skill of theirs every session. Did somebody spend points in 'swim'? Then they're going to have to cross a raging river. Diplomacy? Ok, cancel the ambush, the bandits will bar the way forward and give an opportunity to convince them otherwise. Rather than just giving a bonus to strength, face the player with gates to pull down and arm wrestling contests and having to hold back an avalanche of boulders.
At one point I GM'd a game with first time players who turned out to really, really enjoy being petty criminals. In the first session the crown prince was escaping from an evil uncle. The players were supposed to help smuggle him from the city, and then go on quests for him to consolidate some power, and then he'd rise up and seize his rightful crown. Instead the players promptly sold his location to the city guard. Ok, fine, I took the information about the players and learned I had to lead this group with promises of ill-gotten gains instead of calls to their sense of right. Can your game learn similar things? Give the player an opportunity to help the princess with a minor problem. If they jump at the chance, great, start a love story. If not, are they interested in the prince instead? Or maybe love stories just aren't there bag, and let's get back to the dungeons.
You can get some of this stuff from a survey, but you can also just observe the player for much of it. Instead of saying their favorite stat is strength, you can just see which stat they improve. Instead of asking for alignment, you can give them good and evil choices and see which they take.