CtB was really a good flick, IMHO. Arnie did a good job as a naive young barbarian in civilization, though he was a bit whiny for my taste. James Earl Jones was a tremendous bad guy.
CtD was cheesy, plain and simple, but it was fun in its own way. I ran my PC's through the plot, with a few changes, and they liked it. Plus, the notion of Wilt Chamberlain being charged with protecting the virginity of a Playboy model just makes me laugh every time. CtD was much more of a D&D-style 'adventuring party' movie than CtB.
Never saw the live-action series, though I can imagine how much it must have sucked, like almost every other live-action fantasy or sci-fi series in the history of mankind.
The cartoon was stupid. I only saw a few episodes, but one line stands out in my head: Conan refusing a bath, saying "My mother dipped me in snowmelt from Crom's mountain once a year whether I needed it or not." This made me cringe, literally.