What does this even mean? I assume that you're talking about in a moral sense because of the value judgement you appear to have made.
Of course, when I say 'good' I don't mean in the moral sense. Imagine you were to design a way for people to keep score and they had to use tangible things. What would make one tangle item better than another? Here's a quick list I came up with...
1. Easily transferable. Money fulfills this because it can be transferred electronically. The physical good need not even exist. Money when talking about it as a point system is strictly an abstract. Put another way it is a stored value that can later be redeemed for big macs or Jane Austeen books.
2. It must be difficult to acquire. Money you can't just print (Well you can, but it is mostly worthless). The difficulty makes it more of a way to keep score in the game of life. There needs to be a way to prevent someone from adding to their score arbitrarily.
3. You must be able to keep score at small enough intervals. Keeping score by buying big macs becomes unproductive when you get into the millions of dollar range. At the same time keeping score in the form of luxury cars becomes impossible in the thousands of dollar range.
That's why I said money is good. Not in the moral sense that those who have more money are better people or some form of Prosperity theology. Just that money has many of the traits needed to provide a way to keep score.