I do not think it is ‘unethical’ for the creator of a game series, in this case Jane Jensen, to request of someone that they not make a sequel. Make sure you are just not throwing around the word unethical. If I was the creator of something and someone decided they wanted to continue the story, depending on what it was, I would certainly feel like it was my personal thing and I wouldn’t want them to mess with it.
In any event, that’s completely moot anyway since it wouldn’t matter what Jane Jensen said, though as a fan I respect first of all what her wishes are – it would come down to VU.