Each his own. Edge is pretty much the only mag I care about for actual review numbers. The rest like to work on a 7-10 scale coupled with guaranteed bonuses for franchise history and fan hype.
Edge aren't just harsh reviewers, which by itself woudln't be a problem. They are biased reviewers:
God of War 3: 94 average, Edge 80 (-14)
Heavy Rain: 87 average, Edge 70 (-17)
Uncharted 2: 96 average, Edge 90 (-6)
Uncharted Drake's fortune: 88 average, Edge 80 (-8)
Killzone 2: 91 Average, Edge 70 (-21)
Ratchet ACIT: 87 Average, Edge 70 (-17)
Ratchet TOD: 89 Average, Edge 80 (-9)
Resistance 2: 87 Average, Edge 60 (-27)
Resistance FOM: 86 Average, Edge 70 (-16)
MGS4: 94 Average, Edge 80 (-14)
GT5P: 80 average, Edge 70 (-10)
Ninja Gaiden Sigma 2: 83 average, Edge 70 (-13)
Motorstorm PR: 82 Average, Edge 70
Average: 14.3 points lower than Metacritic
And to prove they are not just harsh reviewers:
Halo ODST: 83 Average, Edge 90 (+7)
Halo 3: 94 Average, Edge 100 (+6)
Forza 3: 92 Average, Edge 90 (-2)
Forza 2: 90 Average, Edge 90 (0)
Fable 2: 89 Average, Edge 90 (+1)
Gears of War 2: 93 Average, Edge 90 (-3)
PGR3: 88 Average, Edge 90 (+2)
PGR4: 85 Average, Edge 90 (+5)
Ace Combat 6: 80 Average, Edge 80 (0)
Crackdown: 83 Average, Edge 80 (-3)
L4D: 89 Average, Edge 90 (+1)
L4D2: 89 Average, Edge 90 (+1)
Ninja Gaiden 2: 81 Average, Edge 80(-1)
Average: 1.1 point higher than Metacritic
I rest my case, it's crystal clear what they are.