Don Parsons writes: "When shooters took RPG elements and added them to the mix, it was an evolution in the genre. That “just one more game and I’m sure to unlock (insert weapon/attachment/camo here)” mentality is an addictive quality for shooters. Few have mastered the progressive tree of unlocks, but two big franchises you can count on are Call of Duty and Battlefield. They both offer incredibly deep unlock systems that can cater to various individuals. I’ve sat down and spent some time (3 hours to be exact) with both games and jotted down some numbers to share."