The most successful pitcher in baseball history is a highly debated topic. Many people argue that it is either Nolan Ryan or Cy Young. Ryan holds the record for the most strikeouts in a career, while Young has the most wins. However, there are other pitchers who have had significant success in their careers.
Some of the other top candidates include: Tom Seaver, Randy Johnson, Pedro Martinez, Roger Clemens and Walter Johnson. Each of these pitchers has had an amazing career with multiple All-Star appearances and records. It is hard to determine who is the most successful when there are so many greats to choose from.
In the end, it is up to interpretation as to who is the most successful pitcher in baseball history. While some may lean towards Ryan or Young, there are plenty of other greats that could make a case for being at the top spot.