I think the point is being missed here by Levine, which doesn't surprise me because "Bioshock 2" got some pretty substantial criticisms on it's writing.
The key to understanding this issue is to realize there is a differance between an ending a few vocal fanboys don't like, and and ending that virtually everyone dislikes.
What's more there is also the factor that this game was intended to be a triology, but Bioware/EA decided to turn it into a franchise, and thus the ending isn't viewed as being art, but as a way of basically not resolving anything in a direct fashion so they could make more money off of it. This is a BIG part of the reception which I think a lot of people are missing.
Then there is the whole issue connected to the above that Bioware made promises involving the ending which were not met.
Like it or not, the "games as art" defense can't be applied to companies just flat out screwing up or a way of justifying profiteering overcoming the writing and design. People saying that games can be a platform to create art doesn't mean that the potential is a get out of jail free card for developers to prtentiously invoke "art" as a defense of anything they want to do.
What's more, art can still suck, really it can. Artists frequently wind up changing their work based on reception, especially when they are working for money.
Look at it this way, if you go to a theater to see a film and it sucks to the point of upsetting the majority of people, those people will demand their money back and receive it. Being "Art" doesn't change the fact that the work sucks. In the case of ME3 once you pay for it, your stuck even if you thinkt the ending was a huge waste.
What's more those creating art not intended for the mainstream typically do so in free shows or to a very limited audience, not as a mass market production like ME3. See, a little independant game costs you nothing but time, or only a few bucks (which in many cases is pushing it), Mass Effect 3 cost you $60 freaking bucks minimum, and $180 or more accross the whole trilogy.
There is no defense for the way Bioware dropped the ball here, none. It's true that they will probably not be able to create a universally rave-worthy ending, but they CAN create an ending that won't be universally hated by nearly everyone.