Global 40 is the big boy, but ironically, I find it a very tight, almost unforgiving game. One wrong move, and bamb! – you are dead. Of course this can vary with skill levels, but playing good players, especially on the league, can turn this game into a nail bitting chess game with dice.
The last 1942 version to come is a respectable game, if a little dull.
Probably the best “medium” version is Anniversary, if you can get it.
But I think the best game for the optimal combo of money down/play length/enjoyment is Pacific 2001. That sucker was great!