Let's face it the game possesses no longevity at all.
Halo 3 had customs and an excellent matchmaking system that kept it going.
Halo Reach had -blam!- customs and an even -blam!-er matchmaking system
Halo 4 has no customs and an even -blam!-er matchmaking system than Halo Reach.
R.I.P Halo
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A year? Watch the population drop off in 3 months.