Unfortunately, and as much as some people dislike Lindelof.....the people behind Prometheus (however much flawed) are big thinkers. Most of the time when these prequels come out, they're hatched by the Studios (corporations) behind them. George Lucas is no different, he made a series of prequel films, however dazzling to look at had ZERO substance.
In order to make a prequel work, a lot of serious thought has to go into how it can be made fresh and not just a retread, which is just what sequels become. Even ALIENS was a retread in many many ways.
I'm obviously hoping for the best when Prometheus releases, and as a betting man, I believe it will deliver in spades, but I'm also wary as well.