Having played battlefield 2142 before Bf 2 i found the gameplay slightly linear compared. The majority of the weapons are too unaccurate and becoming a marksman with each weapon will take a large amount of time.
Nevertheless, the content is there - 28 maps, 100 vehicles and endless amounts of play styles to suit anyone from sniping to anti tank to Medic. The vehicles offer much more variety compared to say COD4 which is basically set in the same environment. The expansion packs really add to the value and depth, especially special forces.
The only other issues is the fact that vehicles dominate. If you get a helicopter of fighter jet at the start of a battle the only way to bring them down is with another heli or jet. Look past this and you'll find an utterly enjoyable FPS with so much variety it makes COD4 look like a game of cards.