Somebody had to start the homer vote (albeit a reasonable one), so I did.

Huh, with only 11 votes cast, I'm the only guy to vote for Randy Johnson, a pitcher I've long admired.  While Santana might overtake him, he's been nowhere near as valuable.  Johnson has pitched almost 400 (FOUR HUNDRED) more innings than Johan so far this century (more, I believe, than anyone else in this poll). 

Since the turn of the century he has:
Won 3 Cy Young awards, and placed second once (2000, 2001, 2002 and second in 2004)
Tied with Curt Schilling for World Series MVP (in 2001).
Recorded ERA+'s of 190, 184, 177, 171 while averaging 251 innings a season (in his four best seasons).  By comparison, Santana has recorded in his four best full seasons ERA+'s of 182, 161, 153 and 151 while averaging only 213 innings a season.

This is a hugely dominant peak, and his other four seasons (including this partial season) have ranged from very good to mediocre - with the mediocre due in large part to the lousy Yankee defence he was pitching in front of.

I chose Johnson over Martinez despite the truly incredible seasons Martinez produced due to durability - Johnson has pitched almost 400 more innings than Martinez.
I chose Johnson over Schilling because I feel he's been obviously better, despite Schilling's Red Sox World Series heroics it's not like Johnson is a stranger to post season success!

Johnson's been the best so far, and he's not done yet.

Since I'm a stickler, I decided that for me, I wouldn't count 2000 (not part of 21st century) in my vote. Taking that year into account, I'd put Pedro and Randy above Santana for sure, since that was Pedro's most ridiculous year, and another great for Randy as well.  With it out, it's a lot closer. A lot of good choices though.