The game is by far the worst in the Battlefield series. At best it offers EA a list of what not to do in the future.
The immersiveness of the game, without making it an all out MMOFPS, the environments the game offered, the perfect vehicle combat system. All of those are amazing featues that made 1942 an instant classic. Vietnam, such a vibrant era of war, that could have been made immaculately into a game. They just failed...plain and simple. The graphics weren't amazing, the sounds were nice but thats just because they had Hendrix blaring. The levels were poorly designed, and the gameplay was far from balanced. It is to this day riddled with inconsistent coding and bugs, and save a few close quarters maps, the gameplay still is lacking to the max. About the only good thing I got from my time playing the game was being able to run over the enemy with a moped.
Now lets look at what they improved upon when making Battlefield 2, and how the failure of Vietnam served as the stepping stone from an amazing game (1942) to a decent title (part 2). The flight system is much improved, where as it was horrible in the past. The vehicles are equalized, and flying a helicopter around doesn't make you a god. Level design is suprisingly good, and most maps offer up a very fun experience, for everyone, from the infantry to the tankers to those pilot-types. The graphics when it was released were just as good looking as every other game out at the time despite the large scaleness of the battles. They really took the mistakes of Vietnam and fixed them.
Question you have to ask yourself is do you really want to experience Vietnam's abysmal lack of..everything, or would you rather just play the other titles in the franchise?