It really depends on the game, sometimes I trust neither and I usually disect reviews to understand weather or not I would like the game. There are a lot of biased and over inflated reviews on the internet out there. Why did Medal of Honor get a 6/10 on some websites while Black Ops got 9/10? There isn't much of a difference, except CoD has a more difficult single player.

Generally I trust reviews more, but there are a lot of fun low rated games out there, like Front Mission, Project Sylpheed, Too Human, Infinite Undiscovery, and Mod Nation Racers to name a few. However these games are generally only fun to me because they are my type of game, so I understand why reviews in general are low. This is why it's important to disect a review. 9/10 for a game like God of War is great, but to me it's a game I could beat in a rental and has no replay value, or even a deep story, so it's not for me, at least not at full price. On the same token, Front Mission gets an average score of 6/10, but IMO it deserved at least an 8/10, it's about the same quality as the first Lost Planet.

Sales are essentially meaningless to me. Lost Odyssey, Demon Souls and Mass Effect 2 are IMO the best RPG's this generation, but Fable 2 outsold them all combined. Gears of War and Uncharted 2 are some of the best shooters this gen, but CoD outsells them both combined on only one of the consoles it is released on. Halo is fun too, but I think the gold lies in Uncharted Gears.

That's my opinion

I tell you why, because the difference in quality is HUGE between these two games.

Black Ops does EVERYTHING better than Medal of Honor. Really everything.

I dont use either since they can both be very biased. sales = mw2 is greatest game on earth, review = gran turismo 5 is worst sim racing game, and both of those are so untrue that its not even funny.