I have to agree with random n00b, "artistic ambition" really isn't very specfic at all.
What is it that would make a game artistically ambitious?
Krezack answered the question well enough, but i can give a comparison to modern movies. Take "Taxi Driver" or "Apocalypse Now!", movies that many consider to be one of the best ever, but are they entertaining? Certainly not, compared to most comedies and action movies, like Die Hard and The Terminator and The Predator.
Those two movies by copppola and scorsese are some of the most entertaining movies I have ever seen.
I think a problem here is the definition of entertaining, entertaining means something more along the line of giving pleasure to the person being entertained and I derive gobs of pleasure from coppola and scorsese. If anything artistry should be viewed as the highest form of entertaining.
Anyway, I like how the people who had to tell us what 'artsitic value' is, did so by using equally vague terms or by showing us something of artistic value. Doesn't really help any of us self-proclaimed art-illiterates how to recognize art.