How a wine changes with aging is a complicated thing. Wines tend to "get better" until they reach a peak and then start to decline. How long that time is depends a lot on the specific wine, the style, how it's stored, how it was made, if it has a lot of tannins or not, etc etc. It is not true that the older the wine the better it is. Wine is a living thing. It is born, grows to maturity, starts to get old and eventually dies.