some rules of art taken from an Art Appreciation class last semester:
1) Art is what the artist says it is. If the artist (developers/designers/game team/whatever) decides it's art, who could claim otherwise and qualify their statements.
2) Art is what the patron says it is. If a user says it's art, then, at least to some person it is now art.
Now for my opinion: When it comes to fringe cases of "art," it's still art if the creator says so. However, as is the case with modern art, art is an expression. And when artist reproduces somebody else's expression, I loose respect for that work. Like Jackson Pullock's spray paintings, when people do the same thing, I'm like, "Really? Wow, you are great at expressing yourself like Jackson Pullock!"
As for video games, as a whole, it depends. But aspects of video games like level design, UX, UI, they are definitely art forms. Especially when done well.