Deftangel's 5 Top Games for 2008 Gamasutra article indicates that the 360 version of Army of Two sold around 800,000 to 900,000 in the US alone. VGC has the game at 1.33 million already. Given that it has sold over a million & is by EA, it will very most likely have a Platinum Hits version release. Given this information, I think this is undervalued.
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