User: Who is the greatest golfer ever?
Assistant: Most consider Jack Nicklaus the greatest golfer as he's won 18 major championships, the most of any golfer.  Major championships are considered the ultimate achievement in the sport of golf.  Jack Nicklaus also has the most runner-up finishes in major championships with 19 and the third most PGA Tour tournament wins with 73.  Many would argue that Tiger Woods is the greatest golfer of all-time with 15 major championships and more PGA Tour tournament wins (currently 82) because he played in a more modern era that was considered to have better competition than the era in which Jack Nicklaus played.  Tiger Woods was also considered to have had the largest impact on the overall popularity of the game of golf.