Replay Value
Halo 4s single player will take around 6-8 hours on Normal difficulty, and invites multiple playthroughs on Heroic and Legendary in order to hoover up those pesky achievements. Its the multiplayer, though, that really gives it replay value; just getting to SR-50 will take 20-30 hours at least, and with new Spartan Ops maps being released for the next few months, theres certainly a lot to bring you back. Black Ops 2s single-player offering, like the other games, doesnt last too long, but this is largely compensated for by the insanely addictive and comprehensive multiplayer offering. With the propensity of Double XP rewards these days, getting to Prestige Mode never takes as long as it used to, but the incentives offered to keep gamers playing past Prestige means getting to Prestige 10 will become a feasible goal for many players. That your weapons arent de-levelled anymore is a huge bonus, and means a dedicated player could very well rinse 200+ hours out of the online alone. Black Ops 2 wins it easily, if only because the online reinvents itself and yet remains fiendishly addictive. Halo 4s is still a cracker all the same, though its Black Ops 2 that will likely keep challenging you long into the new year.
WINNER: Black Ops 2