Played almost every Battlefield game since this one, but this is the one that started it all for me, also for the FPS genre in general, other than maybe Half-Life and Counter-Strike.
Love the other Battlefield games, but none has felt as sandbox-y like this one, and often having maps that are totally unbalanced just to be somewhat accurate to the battle is amazing. It's not as much a competitive game as it is a creative game.