Presuming I had the rights to all three, the 70s game was the best for my money. Though I wonder how many possible ways there are to arrange the board given the rules it has to follow (no blank squares touching, the three of each matching value touching, etc.) Looking it up on the Wiki, the 40s-50s game sounds like it's pretty much a lower-stakes WWTBAM with one wrong answer being allowed in lieu of lifelines; and while I like the concept of the original format of the 80s version it really plays like a confusing cluster**** in practice.
(For that matter, I wonder what's the shortest and longest times taken into the prize vault in the 80s game? The puzzles generally aren't that solvable until at least the 40-second question, but even so, a winning team could potentially have anywhere from 70 seconds to 8 1/2 minutes, which seems troublesome from a production standpoint.)