I would not want to be the employee or manager of your GameStop.

Nope! its you are lucky!

The 50 bucks is probably gonna be on him when someone complains. Honestly, he screwed up. What you did was somewhat unethical but I wouldn't call you a jerk. Especially since you got him to look at the receipt and the console.

The moral thing to do would have been to correct him and make sure you got the version you ordered, or at least paid for the version you walked out with. You took advantage of his ignorance, screwed someone else out of the system they paid for, and got that guy in a lot of hot water. Knowingly.

Hell of a definition for "lucky"

Also hell of a definition for "accident"

there are far important things in life than worrying about if you screwed a corporation over a 50 dollar upgrade which they will still profit from. And at worst made someone wait an extra week for next shipment of consoles.

Hahaha i had pretty much the same thing happen to me when I brought my ps3 was paid for the 40gig gotta 60gig with backwards capability lol

At worst you got someone fired, failure to pay bills, feed self, rent, gas, etc. There will certainly be consequences for that employee, and all the cheering on you get from the internet does not change the fact. In answer to your own question, Yes, you are. It's not somewhat unethical, its completely so.

He won't get fired for that likely he gets written up. And if he does it's not like gamestop clerk level jobs are hard to find...

He made a mistake regardless. Since I've worked in retail before, 99% of the time the customer takes advantage of the situation. As an employee when you fuck up, you fuck up. Something like this aint gonna get you fired unless they already don't like you, or have been written up previously. 

He took someones elses order, it wasnt the fault of the poor guy who is now missing his order

He knew the clerk was making a mistake and should of said what he knew to help the clerk understand, it is stealling

No one knows that for sure. That is not the point, it's an answer as a worse case scenario, but let me give one even worse, you can be charged with a crime if the ATM gives you too much money and you do nothing. It's happened to people before. A mistake doesn't legitimize things like that, you got that system accidentally, you signed and paid for another, they can certainly track you down based on the systems serial number. That is just another about worse case scenario. Nothing changes the fact, to answer the question, it's not only a jerk action, it's unethical and can be viewed as theft. Sugar coating it by saying but this or but that does not change anything.