Hanukkah Solo wrote:
It's not so much that Mass Effect has been Earth-centric. It hasn't, really; in fact, one of the more refreshing aspects of the first game was how unimportant Earth really was, especially compared to other sci-fi settings (like Star Trek) where Earth is the center of everything.
But Mass Effect started drifting back towards familiar territory starting with the second game and its "humans are more important to the Reapers and the most genetically diverse species in the galaxy" stuff, finally culminating in Shepard's trial being held on Earth rather than a more logical location such as Arcturus Station or, even better, the Citadel. If the only reason for Shepard being tried on Earth is because they needed an excuse to have him there when the Reapers attacked, they could have come up with a better one that works within the setting.
To be fair, it seems like the whole point of the "reclaim Earth" thing is to give the galactic war effort a bit more focus than just "save as many people as possible." It makes it easier to build a story arc since you've got a concrete goal (save Earth) on top of the abstract goal (defeat the Reapers) since they're able to guide you through a coherent set of steps to save Earth and then defeat the Reapers.