There is still no formal 8th art, but why should we on Planeta 42 propose the video game to be the 8th art. It is because the process of creation of a video game include all the 7 traditional arts:
Painting: A good video game, require a good graphics, should it be a static picture or a sprite. A lot of artists now become graphic designers in gaming companies.
Sculpture: A modern video game contains a lot of 3D. We may see the 3D modeling as sculpture art, and the 3D modeling software include tools that are basicaly used in sculpturing literally.
Music: What is a good video game without music? Should it be made exactly for the game or borrowed from the many musicians on the internet, music gives atmosphere and excitement in the video game.
Literature: And what is a good game without a good story, a drama or a mistery? Role playing games may be considered a masterpiece in literature, or vice versa.
Performing: Video game performing goes in two ways. First it is the story line performing that is virtual representation of some real performing art. And second is the physical performance, is the game running smooth, is it slow, what computer class it needs, what monitor resolution even.
Architecture: Video game architecture also goes in two ways. First is the virtual world architecture, level design, and so on. Second is the programming architecture - the program code itself is a kind of an architectural masterpiece, or not. Slapy programmers like me, are poor in architecture art :)
Film: Needless to say that every decent game have at least intro movies, and then some use cut scene movies and many more ways to implement the art of filming in the video game creation.