Yes, let's look at numbers. Look at the career list for the following categories: Winning %, WHIP, Hits/9 innings, K's/9 innings, and Adjusted ERA. Tell me where Clemens or even Cy Young are in those categories. Pedro is in the top 3 of all those categories, except where he has just barely slipped to # 4 behind Ryan in Hits/9innings. Also, tell me if there are any other statistical categories that are better indicators of a pitcher's worth. He's not only the best pitcher to wear a Red Sox uniform, but the best of all time. I saw the Rocket from his rookie year and I watched all the big pitchers from the 60's. None of them can claim to better than Pedro.
Edit: These numbers go beyond his prime. His prime was other-worldy, and frankly, his career numbers are close to other-worldy.