For starters, many consumer product reviews are about as insightful as YouTube comments – and that's being generous. Even if they were fair and accurate, Kmart will presumably favor submissions that might help it sell games instead of those that truly inform shoppers. What's worse, there's nothing stopping developers and publishers from flooding the site with bogus reviews, lowering the odds of yours being picked.
It's interesting that the company says its intentions are to "bring the Kmart online and in-store gaming communities closer together," because in the next breath, it says it's looking for constructive, well-written reviews partly targeting an audience that "may be made up of non-gamers." If that sounds like your kind of fun, sign up here and you should be able to post your thoughts about any game on the company's site.