while there's no bad choice in your list, i think Dead Space would have the lowest replay value, making it a good candidate for picking up in a few months when the price inevitably drops. on the other hand, it's also the only choice where co-op isn't practically mandatory. just know that each of these three games has something unique to offer, so you need to know what you're giving up when you choose one.
i personally wouldn't recommend playing L4D or RE5 without another human player.