I think you should use small scenes from several games and explain to your teacher why you think that those scenes are art in your opinion and not just use one big game as a whole.
One that comes to my mind right now is a scene I just played yesterday.
It's from Half-Life 2 and it's the part where you first meet Father Grigori
What I like about that scene is a combination of different things. First, it's the way you experience the part until you get there. You think you're alone in that deserted town, until you meet the zombies. Now you know why the population of that town is gone and you realize that the evil can lurk in every dark corner but you still feel completely alone. It also helps that you play Ravenholm when it's night.
So you're playing through that part, thinking no other human being is here when you suddenly hear a voice but only a voice, you see no body. You're not alone anymore, now you want to know where that voice comes from, you have a goal.
It's a great way how they play with the emotions of the player, that's great gameplay design in my opinion.
Anyway, you get to the part that the picture shows. Just the way father Grigori is being shown in that part is really well made.
He comes out, behind him this light in the normally dark place. Underneath him is a fire where the zombies burn. He's holding a gun and he promises from above the fire that he'll watch over you. He seems to represent a religious metaphor given that his name is
father Grigori, he looks like some kind of guardian angel. The funny thing is that he seems to represent an angel but he isn't at all like the classical image of an angel. First of all, he protects you with a shotgun and later in the game you realize that he has lost his mind while living with the zombies all alone in Ravenholm for such a long time. But still, he's the only "normal" person in Ravenholm besides you, which means that you're not completely alone anymore.
This was just an example of how I've experienced that part when I played it for the first time. And I think, things like that are exactly what you should tell your teacher, things that show the unique artistic possibilities of games. These things distinguish games from movies and books. You experience things differently, the way you can interact with the world is unique in games. The gameplay design is artistically very well made.
In a book or movie, I don't think the part which I just explained would have felt the same. At least the emotions and experience would have been different, not necessarily worse but just not the way it is in the game.
Well, that's just my opinion on art in games but I hope I was able to help you a bit and if you want more games with scenes like that, you could also look for example at Shadow of the Colossus or Bioshock.