I totally understand your reasoning and I confess it crossed my mind as I was writing the original comment. However, I approached the issue in a probabilistic manner. It's much more likely that Bill Gates has a bigger impact on the world than 5 "random" people. Even if those people would eventually have a bigger impact I still wouldn't consider my decision a mistake because it was statistically correct to let Bill Gates live, with the knowledge I had at the moment. Nevertheless, as I've stated above, this argument is indeed a bit extreme and raises questions that go beyond the topic at hand.
Thank you for sharing your opinion.