Funny that you chose a piece of art as your metaphoric example. Because, if I commission a painting of a dog, and the artist takes two years and hands me a great picture of a cat, I am fully within my rights to send it back to the artist and tell him it's not what I paid for.
Now, if you are reffering to sight unseen art, then that is a different story. But then why would you buy a piece of art you have never seen? That's pretty foolish. Same goes with anything else. Cars, food, movies, books. You are lead to believe the car will be good, the food will be good. Here are our reviews, here is a description of the item, here's what it looks like, here's a sample, here, test drive this car to see if it's what you want. No one buys something sight unseen in the real world, unless, you are a gambler. Gambling is a habit based off chance however, and you are not buying a product.
ME3 was supposed to be, for all intensive purposes, be a very good game, with a lot of really great features, and a capstone ending that ends the series and brings closure to the trilogy. Thats what we had been lead to believe, even while playing the game. Instead, what we got was something completely different. A MONTH before buying the game, they told us if we wanted the 100% complete game, we needed to buy a DLC. Then, they went back on their promise of closure, and gave us a shitty ending that can obviously be exploited for future sequels on down the road.
Imagine buying a car, completing all the paperwork, conducting the test drive, checking with review sites, checking the competition, and finally deciding to go for it. Then, at the last signiture, the dealer says, "Hey! This just in! If you spend an extra 15% of the total cost of the car, you can have the spare tire in the back of the car!" Wait, that doesn't come standard? While it does not affect the function of the car in anyway, it's nice to have, and will likely come in very useful. Why is it not standard?
So you buy it, drive it off the lot, and then after 10k miles, the car no longer runs, but functioned flawlessly up until then. WTF? I didn't buy a car, just to have it's last hurrah be a giant piece of shit. Same with ME3.
You don't buy sight unseen, you don't pay extra for that which should be standard, and you don't pay for a product with built in obsolescence.