I studied this briefly in a theological course.
Yes, God is most likely omnipotent. However, even if He has the potential to do anything, it doesn't mean he would. The beauty of Creation is Free Will, and if God was to assert control over everything, humans wouldn't have the ability to choose their own paths.
If God had the ability to do anything, He would've prevented the original sin. The original sin is, as I see it, the ultimate first test of free will. Without free will, there would be no grounds for evil- as God is only good. If there is no evil, there is nothing to compare goodness to and there is no way for humans to live lives that improve and grow. There would be no ultimate incentive to learn goodness through God if everything was peachy.
This is a very big theological question with a lot of different stances, so I'd be interested in hearing what other people have to say.