The more I think about this, here’s my list:
Tom Brady
Bill Russell
Bobby Orr
Pedro Martinez
Pedro is obviously the one who stands out.
Williams played for 19 seasons with the Red Sox while Pedro played for 6. This itself is enough for many to choose Williams. I think that's reasonable. However, I believe Pedro is the choice because what he did in six seasons is almost inarguably the most dominant era adjusted dominance in the history of baseball aside from Babe Ruth's feats.
The only argument amongst baseball nerds is whether Pedro's 1999 or 2000 season was the best in history (and he was better in 2001 before a career changing injury.). He was so dominant it's almost impossible to put into words. We remember how great Randy Johnson was. If you adjust for the peak steroid era and offenses be faced, and look at best 5-7 years, or best 2-3 years, he is leaps and bounds ahead of Johnson, far ahead of Gibson, Koufax, Clemens, Kershaw, Ryan, and Maddux. You can find a lot of these breakdowns on Youtube, Reddit, etc. The amazing thing is that everyone outside of Boston agrees...Pedro is universally worshipped by everyone including Yankees fans, Kershaw fan boys, etc.
But as incredible as the stats are, they don't stack up to the visual artistry of watching the man pitch from 1998-2003. Many have called it a quasi-religious experience. Many have cited watching Pedro as the reason they fell in love with the sport, or fans from other teams converting to Red Sox fans just to follow him and root for him. The way the ball moved off of his alien like long, hyper extendable fingers was a sight to behold. He didn't strike out batters but invalidated their manhood. He had three of the most devastating pitches including the most magical changeup you'll ever see .A little guy under 6' tall with the confidence of god, never giving a millimeter, later admitting 90% of his HBPs were intentional. That windup and delivery were iconic. Pedro is in extremely rare company of other athletes whereby they appear to possess something transcendent and watching them is surreal. Jordan and Maradona come to mind.
So many memorable near perfect games, heroic games, dominant games. 1999 ALDS obviously. 1999 ALCS. All the 17K games. The Yankee Stadium games. It's not a knock against Williams, but Pedro did get his legacy cementing ring and while he had lost his immortality in 2004, he was still solid overall in the postseason and pitched seven shutout innings in the WS.
The Red Sox made little effort to keep him past 2004. Pedro's health was a major concern. I don't see either side as wrong and this shouldn't be a knock on his Boston legacy. He went to Cooperstown with a Red Sox hat and constantly identifies as a Red Sox player and loves Boston. Rarely do you see a former non white athlete embrace the city like Pedro. There are also many stories from people about meeting him. A very jovial, outgoing guy who genuinely likes fans, always stayed longer to sign autographs, etc.
I'll admit there's some personal bias here, but that is kind of the point. Pedro brought out feelings of awe in people. Like Orr, he is a unicorn, someone whose style and "cheat code" level of dominance cannot be replicated.
