Freedom in a videogame is just as linear as freedom in America, you can do what you want, but there are consequences and limitations. Just because you are given the option does not always mean you will risk it. A game's ability to replicate this real freedom and introduces the gray area, gives it the realistic tone.
Freedom is relative to the amount of barbecue's per capita, but also gives way to a realistic environment. In Fallout: New Vegas, you are thrown onto a giant map, with the freedom to do whatever you want, whenever you want. You can kill an entire town with a golf club or have sex with a hooker many times in a row. This freedom, however is really only an illusion. Sure, you can do all these things, but their novelty grows old after a while, unlike playing the main story. The non-linearity really has no real pull in the game, as you are inclined to complete quests, and do what you are told so you can beat the game and move on to the next thing. Running around and doing what you want may be fun for a while, but you will be crawling back at some point.
However, if you are like me and played over 200 hours of New Vegas (The same goes for ever other Fallout game [Fallout 2 is my favorite one]) you tend to enjoy the ability to walk into a town on a whim and finding something incredible, or wandering into some uncharted area and finding a unique and cool weapon or armor. The ability to wander and go at your own pace affects the game's environment and overall tone. A non-linear game like Infamous adds a bit of freedom to it's gameplay. The difference between Infamous and Fallout is the pacing. The Fallout games are slow paced, they have an even distribution of politics and action, and that gives it a more realistic pacing. Infamous, though it uses the same gameplay component of non-linearity, has a different pacing, one where it is all action, and no politics. The try to crowbar in the karma decisions, but those offer a very blatant effect with no gray area, which is what makes New Vegas more realistic, and opens the veil of the illusion non-linear gameplay offers.
In short Freedom and non-linearity in a videogame may not be a mind-blowing gameplay mechanic, but when paced evenly creates a realistic, and in turn, artistic environment and tone. I realize open world games are not limited to the games a wrote about, but they were just the ones I wanted to use as examples. Other than that, these types of games aren't something I want to see all the time, but freedom in a game can be an extremely beautiful and entertaining mechanic when done well in games like Fallout. When done badly like games like Infamous, it can seem tacked on, and ridiculous. So fire up the barbecue, grab some fireworks and tie them to your neighbor's cat before you light them off, and enjoy freedom by sitting on the couch and staring at the TV for 200 hours then crying yourself to sleep when you realize that you will never live up to the you that you wanted to be then staring at the knife in your kitchen and thinking about how easy it would be.
The movie "Citizen Kane" directed by the great Orson Wells is heralded as one of the greatest movies of all time. This is so because of it's innovative techniques in cinematography and story telling. Techniques such as deep focus and low-angle shots, enhance how we see the film. Techniques in story-telling would include flashbacks, multiple narrators, and much more, that would seem to be normal to us, but revolutionary to the people of Orson Wells' time.
Today, a new medium has risen, one that is still seen as childish by some audiences, but also seen as art by others. The interactivity with the media gave video games a huge head start, making it increasingly popular. Now that it's popularity is really increasing, gamers are begging on their hands and knees for the "Citizen Kane" of video games. Something that will revolutionize gaming forever. I tell you now that the day has already arrived. The Citizen Kane of video game has risen, and it is being released with every video game. Well, almost every one. I say that the Citizen Kane of video games came with the SNES, the N64, the PS2, the Gameboy, almost every year video games are being changed, and made better and better.
If you want to relate video games to movies look at it like this; the first video games set a course for the revolutionary as did the first movies. If you look at pong, and "The Great Train Robbery", and then you look at Super Mario Brothers, and you look at Citizen Kane, you can see that creativity was spewing from the creative heads of the video game industry, onto the faces of its viewers (You are sick).
In any case, and on a personal note, I see a movie like 2001: A Space Odyssey , much more revolutionary than Citizen Kane, and in fact, most people, or gamers, say that they want a Citizen Kane of video games, people some asshole on the television said that Citizen Kane was the best movie ever, plus most gamers wouldn't have the attention span to watch it. Those who do and know their shit, hopefully you'll see my point in saying that if you're looking for revolutionary, look no further than your N64.
Lastly, this is just me venting, as I think a grand total of 3 people will probably read this.