In the history of pitchers, I think Maddux and Clemens, rank in the top 5, Randy Johnson being a top 15, and then Glavine as a top 25.
Ah, the ever enduring debate between Maddux and Clemens, a popular debate topic among pitching nerds.
From a purely statistical analysis, I would say Maddux has a slight edge. While being 15 wins behind Clemens, Maddux has a lower career ERA and WHIP. To me, a strikeout is just an out, and the number of strikeouts a person has is not tantamount to their dominance. Yet what impresses me the most is Maddux is one of only three players to have 3000's and having less than 1000 bbs (most likely to be four players if Martinez does not retire). For the past four seasons, Maddux has not walked more than 37 batters. While Clemens has 7 Cy Youngs, a record, Maddux has 4, the third most in baseball history. While some of the awardings to Clemens I don't particularly agree with, a Cy Young Aware shows a pitcher's dominance in a single season, not his whole career. Clemens has actually been quite inconsistant all throughout his Major League career, being plagued with injuries and just not being able to pitch effectively. Maddux, on the other hand, is a champion of consistancy and fitness. Since becoming a full-fledged starting pitcher in '88, he has logged at least 200 innings all but once in 19 seasons. Also since '88 until '05, a streak of at least 15 wins for 17 seasons, a record that beats Cy Young's. Also there is Maddux's defense. Clemens holds 0 (zero) Gold Gloves while Maddux has a record-tying 16. Maddux could become the single holder of the most Gold Gloves by any major leaguer if he continues his excellent defense into the 2007 season.
From a non-statistical standpoint, I'm even more inclined to side with Maddux. Clemens was blessed with a great mid-90s fastball, and he eventually discovered he possessed a splitter on par with Bruce Sutter. Maddux doesn't have any trick or special pitches. Hell, in his prime, he could barely throw 90 MPH with a nice tail wind. Which is what makes him so great. On the mound, Maddux is a genius. His cunning and ability to out-think batters by locating and changing speeds is what makes him so special. He uses one of the most under-appreciated gifts of mankind: his brain.
And another thing with Maddux you can be fairly certain about is that he never used steroids. With Clemens, it's not possible to say: Clemens was implicated by Canseco (who had implicated and had been right about others in steroid scandals, including Palmeiro) implicated in the Grimsley report, and if you look at his recent stats, they parallel those of Mark McGwire, who had a "late career resurgence." To be honest, I don't believe Clemens. I think he's a cheater. So, with much certainty, I am convinced that Maddux is not only better than Clemens, but is the best pitcher of his era and one of the best of all time.