Ahh, Medal of Honour: Allied Assault, my introduction to WW2 shooters.
Now, MOH wasn't exactly a brilliant game, in fact there are certain parts of it I would REALLY avoid playing again, but it was a good game, it has done something that no other WW2 game has been able to reproduce with any decency, the D-day Omaha beach landing. That entire level was horrifying, in some ways it made you feel as if you were there, but that's not even the first mission of the game, oh no, in fact it's the 3rd mission, ok, so there's only 8 missions (correct me if I'm wrong but that's what I remember) but it's still a long-lasting game, the missions are long and varied. They are even somewhat realistic to an extent, and unlike Call of Duty you start off as an American soldier and you STAY that way throughout the whole game.
The medals add an essence of replayability as well, for each of the missions you can earn a medal if you achieve certain objectives that AREN'T listed in your normal mission objectives, all except the mission 3 medal, you get that if you survive, kinda hard to not get it. :P
Sure, the AI isn't as good as CoD either but when you consider what AI was like at that time you gotta admire it.
Overall I would recommend you get the game, it's a good challenge and it's a change from CoD, although I have yet to play any of the exp packs yet.