The title says it all really. Some people may say COD4 but there is no teamwork there. If you get on a big strike at karkand server and join a squad then the teamwork is great.
Ok, the gameplay. The game is very realistic, the guns have different capabilities for damge and accuracy so you can choose a weapon which suits you. You unlock two new weapons after patching the game - Go to the bf2 site and onto downloads, download from ea - so you get a good choice for each type of infantry. Each type of infantry is suited to something - anti-tank destroying vehicles, medics for healing etc. Personally I do best as a medic, I see some people playing assault and others so you have to try them out and see which one gives you the best results.
The rank system is a great idea, I only recently found out about the patch and now the ranking system works. It makes the game that bit more addicting, for instance, I usually play overall about 1-2 hours a day, yesterday when I patched it I played for over 3 hours. Some of the medals and badges are hard to get, if you want to know how to get these, there is a brilliant website if you search in google, it tells you what you need to do to achieve each medal.
I must also mention that strike at karkand is the best map ever. On a big server you end up having a big battle, the best is on either side of the river by the train. It is a great war scenario. Both teams have people running the bridge, sniping, medics reviving. Fantastic. Fast points for ranking too.
The graphics are reasonably good, I have to set them all to low until my new graphics card comes so I don't know how good they can get. Currently running a radeon x850 and the graphics are alright to look at.
The game is well worth the money, in my opinion it would still be worth atleast £20 but because it is about 4 or 5 years old now I think, the price is low, so buy it while you can.