Eh. Reviews don't matter one bit. Although I typically agree with most reviewer's opinions on high-end games, I've found myself disagreeing many many times about lower-reviewed games.
Case in point(s):
Earth Defense Force 2017 - panned by critics, the co-op component makes this game (imo) better than Gears of War. Absolutely amazing game, expecially for $40. The average ranking? 70% from all review sites.
Viva Pinata - A true Rare classic. One of their best E-rated titles, ever. Sales were poor (but did decent), but reviewers were real lukewarm. Reviewers had it in the 83-85% range, but this game is better than Sim City and Banjo Kazooie. Go check out the VP thread at NeoGAF - everyone that bought it, loved it (even Bill Gate's daughter)
Dead Rising - Yes, the save feature was gimped, but outside of that, ultra-innovative and near perfect. Despite this, it was still a middle-of-the-road score of 85%.
Summary: Screw critics, buy what you like, they're always wrong. A few are right about games with critical flaws in design that make some games unplayable. IMO, renting is the best way to go. I've rented somewhere near 70 X360 games, and many many I found myself enjoying far more than the reviewers did. Now, in MSG:C's case, I'd definately rent before buying, because a game that gets sub-50% scores are typically aweful, but if you enjoy it, by all means, buy it.