bwebber, I do not see how anyone could ever legitimately make that claim.
When you compare their career numbers in terms of ERA, WHIP, or other pitching metrics it is pretty much splitting hairs, Santana may have slightly better numbers overall but we are talking about domination from both parties.
It should also be noted that Roy Halladay had absolutely dismal 1999 and 2000 campaigns where he might as well have been a different pitcher. After the 2000 season where he allowed 80 runs in 60 some odd innings he went down to AAA and basically reinvented himself, developing the trademark movement on his fastball that you see today, so it really is only fair to start comparing from this point. Even if you count these years, however, the numbers are still close.
I'm sure we can both agree stats are not everything though...
The deciding factor here is blatantly obvious: divisional play. Halladay spent his career dominating the offensive titans of the Yankees and Red Sox (and more recently the Rays) while Santana fed off tigers and royals teams that were complete jokes in the mid 2000s and some bad Indians teams too.
I crunched some numbers to see how right I was, and lo and behold:
Career Stats vs AL East
Santana: 289.2 IP, 3.73 era, 1.22 whip.
Halladay: 965.1 IP, 3.35 era, 1.17 whip.
Again keep in mind that this includes those dismal two seasons. When you can do that much better over that much long of a time, that is impressive.
The kicker? This should be all you really need to see to close out this argument:
Career Stats vs New York Yankees
Santana: 57.1 IP 4.40 era, 1.38 whip
Halladay: 247.1 IP, 2.84 era, 1.11 whip
Were talking about unbelievable numbers here in a huge sample size against the best offensive team in baseball through the decade. After almost 250 IP no one on that team could figure Halladay out. He clearly steps up his game to his competition, and makes you wonder just how good he would be in the playoffs.
Moving on from the division argument, the 52 complete games to 9 is another focal point. You cannot really put a qualitative value on a CG towards your bullpen, you just have to realize it is invaluable. Toronto is notorious for having one of the better bullpens in baseball with relatively no name pitchers. It is quite simply because they all get to rest every fifth day. How far do you want your best pitcher to go? I am sure any manager would answer "all the way" any day of the year. Well too bad Santana too often isn't capable of that... Halladay has proven again and again he is. Santana doesn't win you games alone; he will likely get you into the 7th with a good shot of winning but there is still work to be done. Halladay will get the job done all on his own, at maybe a slightly less statistically impressive pace in terms of era/whip. It still should not be a question of who is the better pitcher, and who any sane team would rather have.
Roy Halladay > Johan Santana, no questions asked.