Although it may not be the easiest thing for modern ears to interpret, the signifance of Chaucer's work cannot be overstated. For one thing, Chaucer championed the vernacular in his work, that is, the real language of everyday citizens. Prior to Chaucer, works of literature were written in Latin or French; while there certainly were English writings, they did not make use of the vernacular. Chaucer's tales helped bring meaningful stories of life to the everyday man.
Furthermore, due to Chaucer's efforts, scholars are able to discover much about the past through his stories. The people Chaucer depicts, their ways of life (work, love, sex) were not the stories recorded by the elite. We are, therefore, able to gain insight into the middle and lower classes which might have otherwise been lost.