I think that good reviews are useful, but not an end-all. A number of
really poor reviews has a greater chance of killing your title than
a lot of great reviews in helping your title.
I personally think that placement is key. You have to make sure the game is visible. That means spending gobs of money on things like endcaps, better shelf placement and so on. Don't underestimate the power of the impulse buy -- but for an impulse buy to happen, the buyer has to see the game.
Buzz in the gaming community is good, too. Right now, the buzz on Iron Storm is mixed. Some think it's great, some think it's way too hard (based on the demo). If a core gamer thinks it might be too hard, they'll never recommend it to their casual gaming friends, which will also cost you sales.