I think Mass Effect is garbage and rated so highly because it was an exclusive. The future games in the series aren't too much better, and the overrated games are overrated on the PS3 as wekk because it was once a highly praised exclusive series that we now have.
While there are a lot of good exclusives, I think there are a lot of games on all consoles that are praised just because they've exclusive. Here are some for Sony and Nintendo too.
Infamous 1. The first game was decent, but didn't deserve the praise it received from critics and fans. The second improved upon the first in literally every way and is deserving of the praise, though. Gameplay is pretty much the same, but the changes included made all the difference.
God of War while pretty, is my least favorite stylish action series. Even X Men Origins Wolverine is a better game in my opinion, but a series like God of War gets constant praise when you'll almost always be using square, square, triangle, or a long variation of the exact same move,plus R1 and Square, or on the original, R1 and X. Games that are highly deserving of this praise like Lords of Shadow, Dante's Inferno, and DMC DmC get overlooked for some reason or another and this series gets massive praise for being God of War.
Animal Crossing. Go around the entire town shake all the trees, find bugs flying around, stuff lying on the ground., then after you've done all you can, talk to one villager who asks you to talk to another villager, repeat. Five minutes of gameplay you constantly repeat. Every game follows this exact same formula and every game is massively praised. How is this fun?
Mario Kart. I hate this series. Playing normally the game penalizes you for being a good player. What's the point of being in first place when you'll get first just by staying in third or fourth?