so if one establishes the daily 5 prayers but still involves immorality such as adultery, does that mean his prayers are not accepted??
We cannot say for sure that ones prayers are not being accepted. But all I can is for sure, may be you're not praying/remembering God from the bottom of your heart. And....
And whosoever turns away (blinds himself) from the remembrance of the Most Beneficent (Allah) (i.e. this Quran and worship of Allah), We appoint for him Shaitan (Satan - devil) to be a Qarin (an intimate companion) to him. (Qur'an 43:36)
So, it can be said that performing evil things in spite of praying can be said is a consequence of not remembering God from the bottom of your heart.
So, remembering Allah in the Salah, with complete devotion is as equally and more important than just praying merely.
Helpful, "How to love saying prayers (namaz)?"
May the creator guide us all.