While it has everything that made the original great, Battlefield 2 builds on that formula and makes everything that much better. The modern setting makes for something us younger folks can more relate to, and just makes for all around faster firefights. Vehicles such as the assault buggy let you whip around the field of battle far faster than the jeeps and bikes of the original, and tanks pack more of a punch this time around.
Maps are varied, and go from sandblasted desert towns to heavy combat on a highway interchange. There's super small maps with tight spots, and large open ones where dueling tank battles across empty fields are commonplace, and fun as all heck. The amount of equipment on display is awesome, with accurate modeling for all the weapons and heavy metal.
Graphically, Battlefield 2 is a massive step forwards for the series, and it looks nothing like the original. The game ran great on the ancient computer I used to have, and just screams along on the hardware of today. The game is, at this point, starting to age, but it still looks and plays just fine.
I definitely recommend this one. You can't really go wrong with any game from the Battlefield series - there's a reason so many gamers have played them.