Ever notice this?
I've noticed it a few times, often with the side/promo games being more addictive rather than better technically. Sometimes the actual game seems little more then mediocre and the side/promo game is incredible.

One example for me was Dark Void. I played it, I tried to like it, but it didn't have enough to hook me. Then I played Dark Void Zero (DSiware/iPhone), a game marketed as a lost Dark Void game from the NES age (though not really) and it has me completely hooked.

Got any others to share?