Within the first 50 there are a lot of "Are you shitting me, really top 50?". Both Mass Effect games, Portal, overload of Final Fantasy, Fallout 3, Eldar Scrolls Oblivion, MGS4 and Bioshock fall into this. Regardless of ranking, these made top 50?!
Nintendo is heavily represented with 15/50, not counting the Rare games(-2), but including pokemon(+2) and retro (+1).
Otherwise this has a surprising amount of historical depth as Ian has pointed out, although it's still pretty shallow, but it is based on popularity, not historical significance.