2 and a half years ago, I got back together with my ex who appears to have had a similar position to me than your ex has to you. I really wanted her back and compared other girls to her all the time. Well we tried but December we broke up again. In 7 years our personalities changed too much and we just don't fit together anymore.
So my conclusion is that you probably should forget about your ex. I know that this is a useless advice but it's most likely good advice nonetheless.
After the failed attempt I'm now moving on. Living alone in my place feels wierd since I have never lived completely alone. First with family and then I always had a gf in my place. Glad I still have my cat though.