PowerMonger, eh? Just to refresh your memory - and (er, thumb, thumb) mine - it's (ah, got it) a rather splendid strategy game from Bullfrog that takes Populous's 3D landscape, spruces it up a bit, and adds in lots of little buildings and men running around. And the WW1 Edition? PowerMonger's unlikely assortment of islands has been replaced by a proper map of Europe, ripe for invading, and your Captains now sport peaked caps and moustaches. Boats have been swapped for biplanes and tanks, and the rest of the weaponry has been updated accordingly. Oh, and the sheep are now deer. Other than that, it's business as usual.
To be perfectly honest, I'm not sure this represents enough of an advance over PowerMonger. True, battles are a lot more exciting, with proper explosions. But the rest is essentially cosmetic. I reckon you'd want to have cash coming out of your ears to lay out for this too.
A smashing game, but PowerMonger always got along fine without it.