Advising one who does not pray

If your friend is mentally sound, then all you have mentioned about him indicates his disrespect of prayers.  If he means what he says, then he would perform his prayers.  His claim that he likes prayers is not truthful; if it were, then he would perform them accordingly.  In fact, the following verse from the Holy Qur'aan applies to such a recalcitrant and unobservant person (interpretation of the meaning):

"Then there has succeeded them a posterity who have neglected and lost the prayers, and followed their lusts; thus, they will face devastation (on the Day of Judgment, i.e., he will face Hell)." Surat Maryam 19:59.

By completely ceasing to perform prayers, a person is judged to be a kaafir, based on several ahaadeeth of the Prophet  (peace be upon him), one of which is:

"The obligation and pact between us and them (the munaafiqeen, the hypocrites) is the prayer, so whoever abandons it has indeed committed kufr (i.e., become a kaafir, a non-believer)." (Tirmidhi, hadeeth #2621, and it is sahih)  The meaning here is that the hypocrites are guaranteed their security and immunity from being fought by the Muslims as long as they perform their prayers; if they abandon their prayers, then they are among the kuffaar, and are subject to being fought and killed in the war against them.  The Prophet  further says, "What is between a person and committing shirk (associating partners with Allah) and kufr (disbelief) is abandoning the prayer." (Sahih Muslim, #82)

The man in question, accordingly, is to be shunned–no one should eat the meat he slaughters; he is not to marry a Muslimah; he is not to inherit a Muslim relative; he is not allowed to enter Mecca; upon dying he is not entitled to Muslim burial rites such as the washing of the body or the shrouding or the funeral prayer; and his inheritance is to go to the the community fund and not to his inheritors. Thus, it is incumbent upon you to exert as much effort as possible in advising him and admonishing him concerning the gravity and danger of his crime, and of the punishment of Allah the Almighty.  If he persists and rejects your admonition, then you would not be wrong in abstaining from your friendship with him, until you can solicit help from other friends among those who accept guidance so that you may spend your time with them inviting him to Allah.