The game that started the Battlefield franchise is damn good.
Okay, let's try to not focus on the single-player. It's basically non-existent in this game. You play through all the maps and that's pretty much it. Now the multi-player, that's a different story. The multi-player is fantastic! Driving the vehicles is still good as ever, as it actually gives it the angle that you would see if you drove a car or plane or boat in real life. Driving a plane takes a while to get used to though, but at this point, there are plenty of people who are experienced enough to fly the planes with you on-board.
The maps are just plain massive for a game this old. You can run around on the island just shooting people, you can drive a boat with a passenger who shoots at people on the island, you can snipe from a much smaller island off the coast of the big island. There are just so many ways to play, you'll want to keep playing until you experience them all!
This game does have two expansion packs, The Road to Rome, which mainly adds five to six maps if I remember correctly, and Secret Weapons of WWII which adds a couple of maps which have new vehicles, weapons, and jet packs! Get them both. It's worth it.
This game is one of the few (along with Call of Duty) that can last many years and still be a great game. Plus, it started a series that has never had a bad game. You need this game in your collection, especially if you want to be a veteran in Battlefield Bad Company.