Why is entertainment such a dirty word? It isn't ok just to create entertainment you have to be creating ART! In a couple hundred years nobody is going to have a gallery with Half Life 2 on demo mode in it. Sure it takes some creativity and a lot of hard work but so do a lot of things.
I guess game designers just want to know if it's ok to be snobby and pretentious, and start putting their names before the game titles... Oops too late, better start calling it art then!
Then again, with some of the things I've seen in museums they might as well call it art. That just proves how arbitrary the label is in the first place, though.