I recently did a mock draft in which I detailed who I believed would go in the top 10 in addition to who their best major league comparison is. However, the best player available is not always selected.
Teams have different positional and organizational needs. Some players have college scholarships that make them more difficult to sign. Others require teams to go well above slot to serve them. With that being said, it is obvious that some very talented players need to wait a bit longer than they should need to until they get selected.