Given the WoTLK Classic Gold benefit of hindsight, we can look back at World of Warcraft 's incredibly popular online multiplayer and see what a big factor the addictive XP and perk system played in its success. At the time, so much fuss was made about the move to modern day weapons and hot zones, and while that certainly played a role, what really pushed CoD4 to the top was its bold refusal to...