Good question. Though it won't affect my response, i am curious as to your personal beliefs, if you're comfortable sharing them.
As for me, i think you've just found a major kink in the reasoning of many people. i've recently been introduced to Buddhism, and it is the first 'religion' i've encountered that asks nothing in return. There is no god to worship, only a man's teachings to follow, and he didn't even ask his followers to believe, only to contemplate his ideas and decide for themselves. The christian God, on the other hand, expects his followers to believe his word without question. The theology glosses over a great many stumbling blocks that would otherwise lead any rational person to seriously question what is going on. You're point that God need not have created us, and probably only did out of his desire to be adored is, in my oppinion, yet another of these stumbling blocks. i'd like to hear how a devout christian would defend this particular question mark