And by the act of "HBOing" I mean taking an existing book or old franchise and turning it into a qualty show.
I think Dragonlance (not the expanded universe, just the original 3 chronicles) could be something special if given the GOT/LOTR treatment.
The Jon Shannow series by David Gemmel would be great, a mishmash of western/fallout with a supernatural theme. It already draws heavily from Shane and Pale Rider.
Also, Journey to the West would be fantastic. It's been done a few times in the East, but an updated retelling in English is overdue, though not to sure how it would be accepted in the States as old dubbed NTV series from the '79+ was more of a commonwealth thing so maybe some of the Canucks will recall it.
Interested to hear what other people have been dreaming of.