Clearly the PS3, it had one of the worst console launches in history. No games, bad online, really high price. A good bit of people didn't think the PS3 would make it past it's 2nd year.
Now look at it, tons of exclusive games and still the biggest ones yet to come out, sales are picking up quite a bit, third party games looking a lot better, finally at an affordable price. In the last three years the PS3 went through a lot.







