Making computer games an educative subject

Please nominate for me browser-based games which would be educational to do a rhetorical analysis on in a classroom/computer setting (and/or ideas on how to teach freshman composition in an awesome way). I'm thinking of proposing an experimental section which would use computer games, and while I guess I could require students to buy a game, I'd rather use free ones if I can.

Current candidates:
Level Up!: The "story," characters and game rules mess with traditional game conventions. It "says" things about time and learning. It aims to please multiple audiences.
The Company of Myself: This puzzler gets kind of hard (I'm stuck on the one where they're like "timing is important"), so I'd be reluctant to expect students to get very far, but I like how it also messes with time and repetition. I wonder how similar it is to "Braid" (another game I want to play, which costs actual dollars). I like that it doesn't shy away from being hard; it's not meant to be a mindless game.
Flash Portal: The first few levels introduce the paradigm-shifting portal system. Later on you just have to be fast at making portals, which I find less cool. Their audience is probably, I don't know, fans of Portal or people who wanted to play Portal.
Radical Play: A somewhat annoying racing game. The cool part is you can win by crashing into the other cars or by winning the race. They don't even pretend to use real physics, which is funny, and doing flips to get points or energy (I don't recall) is kind of fun.
Super Energy Apocalypse: Gameplay isn't terribly original, but it has a complex message - we need to defend ourselves but we also need to take care of our waste to prevent zombies from taking over.

Okay, so what would we do with these games in the classroom? It's possible to do a classic rhetorical analysis (RA) - who is the target audience, why are the elements of the game fun (instead of persuasive?) for that particular audience. Are computer games persuasive, and of what? Could writing about computer games prepare students to write in other contexts? Currently we write on a bunch of op-eds for the RA, which seem to me just as irrelevant to most majors as computer games.

Also, I was thinking of just single-player browser based games that a student could beat in one or two sittings, but could a MMORPG be helpful in a classroom context? We could be part of the same guild in KoL, and it would be fairly easy to track student progress... okay this is getting weird, I'm not sure how/if that would work. Have you played Crimson Room? That might be too hard or too easy to get a walkthrough for. Well, now you know what I've been fantasizing about: playing computer games in my classroom.