1. Walter Johnson: Just look at his numbers. Holy
2. Sandy Koufax: One of the biggest tragedies of all time is that Koufax didn't have a full career to dominate. It took him a couple seasons to take off, but once he did, he was unhittable. From 1961 to 1966. An average season for him was 22-8 with a 2.19 ERA. Pitchers peak differently than hitters. They get smarter as they age. There's a good chance Koufax would have had at least five more fantastic seasons.
3. Greg Maddux: His numbers aren't as imposing as some of the other players on this list, but the era he pitched in was different too. In the '90s he had a 2.59 ERA and averaged 19-10. This was the same time Mark McGwire, Sammy Sosa, Jose Canseco and others were putting up inhuman numbers. There weren't a lot of pitchers who excelled in that era.
4. Lefty Grove: Grove's baseball reference page is one of my favorites to look at. He has the only page that makes regular stats look awful. from 1929 to 1932, Grove posted ERAs of 2.81, 2.54, 2.06 and 2.84, before ballooning to almost a full point above his ERA during that stretch... all the way up to 3.20.
5. Tom Seaver: All you need to know about Tom Seaver is that he came in the top five of Cy Young voting, eight times, and the top ten ten times. He also posted a career ERA of 2.86, and led the league in strikeouts five times.
6. Bob Feller: There's a very good chance that Feller's career would have been remembered differently if he hadn't had to serve in World War II. his three previous seasons before he had to serve our country his ERAs were 2.85, 2.61 and 3.15. Had he pitched in those four seasons he lost, there's a good chance he adds about sixty wins and some extremely good seasons to his resume.
7. Randy Johnson: Johnson is a perfect example of how pitchers age differently. From the ages 35-38, Johnson had a ERA of 2.48 and a WHIP of 1.044. The Big Unit was also quite possibly the most intimidating pitcher of all time, depending on how you feel about the next guy on this list.
8. Bob Gibson: Now here's another intimidating pitcher. Even though he peaked in the year where pitchers dominated because of the mound being raised, there's no denying that he lead the league in almost every category that season. The rest of his career is pretty good too, posting a career 2.91 ERA.
9. Grover Cleveland Alexander: Alexander was one of the best pitchers of the dead ball era, leading the league in ERA five times, as well as WHIP another five. His win totals are a bit hard to swallow considering he won 30 games three times, which wouldn't happen in today's MLB. However, he did lead the league those years, showing that he was better than his contemporaries.
10: Warren Spahn: Spahn along with Johnny Sain anchored a somewhat less than stellar Braves rotation to respectability in the '50s and '60s. Spahn was a model of consistency, never dipping under fifteen wins from 1947-1963.
Honorable Mention: Cy Young: I have no idea what to make of Young's career. For every good there seems to be a bad. He has more wins than anybody else, but he also has more losses too. He has the most innings pitched ever, but he also has allowed the most hits and runs ever. Was Young great or just someone who pitched for a long time? Let me know in the comments.