Aleinu l’shabei’ach l’Adon ha’kol. It is our duty to praise the Master of all.
The Bnai Yissaschar quotes a tzaddik echad, righteous sage, who offered a powerful insight into why we recite Aleinu at the end of our tefillos. Nobody is perfect, and no one’s tefillos are perfect. We (for the most part) are deficient in the proper kavanah, concentration, devotion that we should express when davening to Hashem. Additionally, our lack of the proper fear and love of Hashem that should guide our lives is reflected in our davening. As such, we acknowledge that our davening is far from perfect and probably misses its intended mark. Yet, despite all this, we praise Hashem that He chose to create us as members of Klal Yisrael. Whatever our paucity in prayer, maybe it still rises above any prayer that emanates from the gentiles, because they do not ever pray as we do. With all our inadequacies, our prayer to Hashem still has greater meaning and value than anything they could express.
