I'm pretty sure the only appropriate response to a critic who says that the value of a particular piece is entirely subjective is, "so why the @$#% should I listen to you?"
If the holder of an "opinion" can give ten clear, approachable, and arguable reasons why 'x' is good, bad, or better than 'y', that is of value, and deserves consideration and respect. "That's just your opinion" has become one of the laziest and most irredeemable arguments on the Internet.
I'm not inclined to hate on ME3, it wasn't the best but I definitely won't write off the series.
I don't think that it is as intellectually insulting as what people made it out to be, there is decent subtext and I get that the writers wanted to bring a more Sci-Fi novel level of symbolism, suspense and shock and tried to give the fans some room for interpretation and reading into the subtext. The problem is that it doesn't really work for a AAA game and people wanted rewards for their actions and not care about the origin of the thing 'they hate'. We didn't get anything else, so we need to take the good with the bad.
I always found the ending to FFVII disappointing though, and it was clear that Square did as well... considering the 20 minute ending to FFVIII.
Endings usually suck anyway, I thought that the moral behind Bioshock Infinate was utterly depressing, though I don't know if the way I interpreted it was how it was supposed to be interpreted. But in the culture that we live in how, there's always going to be a hive mind and people side towards the one consensus that the majority makes, rather than having your own thing.