Both games were from companies who are only shadow of their former selves. Overall I hold FFXIII in higher regard as the game had a more unique world and an excellent combat system.
Final Fantasy XIII was mediocre, but thats been my opinion on every Final Fantasy since IX (which was fantastic), Final Fantasy X is the most disappointed I've ever been in a game to date, never had I seen such regression in a series, it was a devolution from Final Fantasy IX in almost every aspect. Then Final Fantasy XII, that game just depresses me as I can't believe the Tactics team made a game I loathe despite the game having parts which were revolutionary to the JRPG genre; I suspect the problem was that after the colossal disappointment of FFX and hearing information on FFXII I had hyped myself up too much, ultimately I give them the benefit of doubt as Matusno left development mid way. Then Final Fantasy XIV, the worst of all, lets not even talk about it. But then I go into the "Will you buy FFXIII-2" thread and almost everyone says yes, even people who didn't like FFXIII and I realize that with such stupid fans that eat up anything you throw at them why aim to improve?
Next Bioware, ME2 sent alarm bells ringing in my mind and then Dragon Age 2's atrocity (and now the well documented terrible reception among fans) has confirmed my fears of where this company is going. ME2 was a hollow shell of an RPG, a terrible one, with absolutely no story, strategy, nothing. A few good characters, clunky shooting mechanics is what Bioware has come to now, but lo and behold it ends up getting a higher metacritic score than Dragon Age Origins; a game that did almost everything right.
Either way no Final Fantasy or Bioware game will ever see a day 1 purchase from me regardless of the critical acclaim their next titles get unless I play 2 games in a row from that series/developer that I love. /end rant
To answer the question in the topic, it comes down to brand name, quite honestly both games don't deserve the sales they got; in ME2's case it doesn't deserve the critical acclaim either.
