Much like fellow bloggers/Whophiles Siskoid and Rich, I sometimes think new Who is enjoyed at the expense of classic Who. For me, classic Who is to new Who what a good stout is to American beer - you can enjoy both, but one is meant to be savored.
This season has seen a more conscious effort to integrate classic Who mythology (and just in time for the 45th anniversary!) - with its focus on moral choices, on paths not taken, this season draws very heavily from two classic Who stories.

The first is my personal favorite story - the one that got me hooked on Who in the first place (and quite frankly, the one where RTD is pulling most of this series' themes). Genesis of the Daleks is a story that is steeped in morality and ethics - in fact, at the very beginning, the Doctor is given a mission by the Time Lords: stop the Daleks before they become a threat. (Or, to use the old chestnut which is quoted, "If you could go back in time and kill a ruthless, evil person while they were a child - would you do it?") Characters spend time discussing choices - from removing emotions that would make the Mark 4 Travel machines more efficient, to hating someone because they're attractive - and somehow, it makes for thrilling drama. When the crucial time comes for a choice, the Doctor asks himself, "Have I the right?" - for many of us, it would seem an easy choice, but the ramifications (only hinted at in this season's "The Fires of Pompeii" seem monumental.)

However, a much earlier examination the Doctor's morality - and a crackling good story - can be found in 1973's Doctor Who and the Silurans. (Available both by itself as well as part of the Beneath the Surface boxed set). Set during the "UNIT era", this story tells the tale about a lost race of reptiles who evolved long before man...and who want their planet back. (The What Lies Beneath featurette helps place this story in a historical perspective). Throughout the course of seven (!) episodes, we see both sides - Silurian and human - debate whether they can coexist, or whether there needs to be wholesale genocide of another race.
I know, some of you are saying to yourself, "Gee, Gordon, these are long episodes - new Who fans won't want to watch these really long stories." But one of the advantages of these - the one which gives classic Who its edge - is that the Doctor serves as an absolute moral force. Granted, you can argue that the Time War made the Doctor's life ethically more complicated...but these are both stories where the Doctor seems to stand for value. Plus, at their extended pace (Genesis' six episodes, the Silurians' seven episodes), they allow for a much more thorough style of storytelling, and don't feel the need to cram a ton of detail into 45 or 90 minutes. (Yes, I'm talking to you, Stephen Greenhorn!). Plus, watching these shows is like enjoying a fine gourmet meal - you can like McDonalds, but sometimes, you want a nice, well-cooked steak. Or chicken).
But enough of that - I know, I know, you're all waiting for the season finale, unless you were smart enough to legally obtain it early. Since you have until Christmas for new Who - and only four specials in 2009 - this is your chance to help your new Who loving fans play catch up.
You'll thank me later. Honest.
Genesis of the Daleks: Highly Recommended
Doctor Who And the Silurians: Highly Recommended