I have no doubt that video games are art.
Games is the mixture of every "traditional" art type with the ability to controll it and experience it. In some aspects you could argue that games are still considered a tool, or simple entertainment. I feel this can't be entirely true as classical music were made for specific functions, but now are highly regarded works of art. Same with ancient pottery (as mentioned.) The notion that it has been made by more than one person can't be right, as most of todays greatest monuments were made by hundreds, maybe thousands of people. Think of the great pyramids, Sagrada Familia (and still in progress). Even in the case where there was one man/woman giving orders and presenting his/her vision, isn't that what a director does? A combined piece is still something on it's own.
I reckon this is split into two questions. What you regard as art, and what the art-institutions regard as art. In many cases the general public will change it's view on art once it becomes official, when an institution comes to the conclusion that a certain method of expression is to be regarded as something fantastic on it's own. I doubt everyone in the world knows why Mona Lisa is to be regarded so highly, regardless if it should or not.
When it comes to games, it's common to only compare the medium to certain games, putting everything in the same box. Paintings have sub-categories, do games? Is Pac man the same as Fifa 2006, Final Fantasy, World of Warcraft or Solitaire? In most RPG's you have a story to tell, music and aesthetics that could in some ways send a message like a painting. What about freeroaming games with no ending or goal? They don't have a story, but have messages and an altered reality of yourself that do create an emotion or trail of thought. But what about the really small internett or board games? Can everything be regarded as the same thing?