a long time ago and also because I think Stuart Robertson has already spoken what I think is the real truth of the matter: D&D is "a cultural Borg ... that rolled around borrowing from just about every source it encountered." Understood this way, D&D's Christian elements aren't much more deep (or shallow, depending on one's point of view) than those of any other religion or belief system from which the game borrowed.
The main thing about this topic that I'd say remains of interest to me is that, in the late '80s, when TSR whitewashed D&D in an effort to avoid criticism from some quarters, it was, in some ways, simply extending Gygax's own belief that there were topics he considered inappropriate for inclusion in a mere roleplaying game. Consider that, despite the inclusion of lots of devils and demons in the game, there were never any official stats for Lucifer/Satan. Likewise, when Gary felt the need to balance out the minions of cosmic evil with minions of cosmic good, he didn't call them "angels" but rather "devas," "planetars," and "solars." And, while there are crosses aplenty, there are never any crucifixes. Granted, the motivations behind what Gygax did and what TSR later were quite different but the effect was largely the same: to keep the game's Christian element largely superficial.
None of this is intended to deny that there are undeniably Christian elements in D&D, but I don't think those elements bring with them many doctrinal/theological assumptions -- or at least not many more than, say, the horn of Valhalla or rakshasas do for Norse paganism or Hinduism. And I've never had any problem with that.