Wow... If we thought like you did throughout history, we wouldn't have gotten very far. No offense. It's intellectual laziness on your part. To get to the point, you are not able to show that the chances are too small for a beneficial mutation to occur. In fact, its ridiculous to rule this out, and you are committing a logical fallacy, once again: "proof by assertion." If you have no evidence for something, you don't get to simply assert it as fact. Again, intuition does not count as evidence. It may be unlikely, but given how much time has passed since the earths beginning, and how many times animals have mated or divided, it becomes more and more likely.
The answer to your question is quite simple. it is more probable that a mutation is either neutral or harmful, simply because what constitutes fitness for any given animal is a narrow set of features. Relative to the possible mutations, only a narrow set of mutations would actually increase the chances for an organism to survive. Therefore, it is more statistically improbable that a random change in the alleles will produce anything desirable, than something undesirable. Occasionally, we do see people with beneficial mutations, but we might not even notice it. They may simply be the "prodigies" we all admire. By definition, any mutation we see, wouldn't be a huge mutation, because that's not really possible, or highly unlikely. It would be a small mutation, something we might not even notice, like greater intelligence, or a greater proclivity to understand math or music, english, etc... who knows. You seem to be expecting someone with wings or something ridiculous, I am guessing. Of course we are going to notice the harmful mutations, while any beneficial mutations might not be noteworthy. They may simply be a very successful person who don't even realize they have a beneficial mutation. So, you have no way of tracking how many beneficial mutations there are, because of confirmation bias with respect to the evidence.