how much would a original final fantasy 7 be worth?

We have an original one too. Here in the UK they sell for anywhere between £20-£30 depending on the condition but it may be different in other countries. As to whether you should sell it, that is a question only you can answer. They could be come rarer or more desirable in a couple of years but then may not. With the next FF due out next year maybe that could influence the price of previous ones.

It all comes down to how much someone is willing to pay for it. At least that's what I think. You have to also take into consideration when you purchased your copy. Did you get it around the time when the game first came out or is it one of the newer copies. So, the older the better. It's worth more as a collectible item. Last time I looked, I saw one for sale for $70 and it was a used original one. It might be worth more down the road but I'm not too sure. After all they keep on cranking out newer versions of the same game so if someone were looking to buy it to play I know for a fact that they aren't going to want to spend that much for it.