4. Battlefield 3
Battlefield 3 is compared a lot to the COD series, although the multiplayer parts of the games are the complete opposite when COD focused on small maps, and fast-paced action, Battlefield focused on larger maps (mostly expands as objectives are completed) with slower but still action-packed gameplay.
Battlefield excels at teamwork based victory, as it is really hard to win the match by just going and gunning everyone. And having the class specifications makes sure that you will have to work together, because you will need a medic to heal up, or support class to have your ammo or even the engineer to fix or destroy vehicles.
Add the level of possibility and unlocking new gear, attachments gives the game a sense of purpose, as you inch towards your new gear makes it feel like you are accomplishing something after the battle. The game is never lost, as Battlefield allows a lot of battle strategies and almost every situation has some way to ensure that you can be victorious.
Plus, with vehicles like tanks, helicopters, jets and other types of transport gives the game some versatility, making it less boring as it may not be fast paced shooter all the time and that adds a lot of enjoyment and fun.