While I have not studied other religions, one thing that has struck me as unique about Orthodox Judaism is its concept of "Kol maasecha yihiyu l'shem shomayim", that all of deeds should be done for the sake of heaven. This concept creates a belief system where there are no neutral actions. Many areas of daily life are codified into law, which means that as one goes about his or her day, there are countless opportunities to do a mitzvah or an aveira. There are mitzvos governing almost every aspect of daily life. Additionally, every choice that one makes, even in things that are not expressly required or prohibited by Torah law, are either meritorious or sinful based on their intent.
It is easy to see the appeal of this belief system. This concept essentially means that every action that every ordinary person does has great cosmic significance. A person who believes this feels that at any given moment, his or her actions can help determine the fate of the universe. It is the nature of people to want to feel important, and this belief clearly nurtures the feeling that each individual is in fact important. Additionally, this belief gives one a ready-made sense of purpose and a goal that one can strive towards.
However it seems to me that this aspect of Orthodoxy, which arguably is the religion's greatest appeal, is also its greatest flaw. Having one central goal as the basis of everything creates a system where nothing can be done or enjoyed for its own sake. Everything must be done for an ulterior motive, that of serving God. One can never truly relax when one must keep in mind that the only purpose of the relaxation is to serve Hashem.
This is particularly troubling with regard to personal relationships. It is written in Pirkei Avos, "Ahavah shetaluyah b'davar, sofo l'hisbatel", that love that is dependent on an external reason will ultimately end. In Orthodox Judaism, relationships, just like everything else, are meant solely as a means of serving Hashem. This can be seen quite clearly by the brachos that are given to a new couple, that they should build a "bayis neeman b'yisrael", a faithful Jewish home, which is in stark contrast to the references to the focus on love at a secular wedding. The shidduch system is consistent with this line of thought, in that people marry based on a list of desirable qualities rather than love, which is not supposed to develop until after the wedding. If one views marriage as a means to an end, such a business-like system is ideal. However, if marriage is meant to based on love and acceptance, this arrangement is clearly lacking.
On a more global level, this concept of a singular life purpose effectively replaces normal human thoughts and emotions. Can one really experience love, empathy, desire, or joy if it must constantly be done for an external motive? If halacha mandates what one should think and feel, does one ever really experience those thoughts and feelings to their fullest?