Generally speaking, whether a wine improves with age is dependent on many things, but is most often determined by its "structure" - the balance acid, fruit, and tannins. As wines age each of these characteristics diminish, changing the flavor of the wine. Since the changes in each occur at different rates, there will be a certain point at which an optimum balance is achieved that makes the wine taste its best. Of course, many other things will also change within the wine over time that affect the taste, so a wine that reaches its optimum balance over 15 years will likely be more interesting than one that finds balance over 1 or 2 years. However, no guarantees can be made with respect to enjoyment, just variation :-).
Most inexpensive wines are meant to consume immediately, which means that more time in the bottle will not likely yield a better balance between fruit and tannins. However, since other things within the bottle may change as well, there's nothing to say that aging won't yield a better tasting wine. However, its pretty much impossible to predict these things, so best to drink up now and save the cellar space for wines that really do have potential.