Did someone really just compare Bioshock to the best selling shooter game of all time? Of course Bioshock didn't sell well on the PS3, since there was no motivation to get it. Call of Duty 4 on the Wii has motion controls and online. The comparison is too flawed.
But MWR is doing great, and I'm definitely considering a purchase when it drops in price (plus, there's a bunch of other games to buy too).