Sufis are a good example of manmade efforts to seek a personal relationship with God. I do not know how successful their attempts are because I do not have personal contact with any Sufis.
Personal encounters with Jesus however are not usually the result of our own efforts. The many witness stories I have come across involve Jesus making Himself known in surprising and unexpected ways. This is particularly true in the case of Muslim and Jewish converts to Christianity where they are overwhelmed with the Love of Jesus in contrast to the remote, distant God of their previous faith.
So I must confirm that my personal relationship with God in the person of Jesus Christ dispells any doubts I may have over my Christian faith.
From what I understand, Sufis claim experience of Allah through their practices, just like you claim personal experience of Jesus. What is the common factor here ? People have all sorts of mystical experiences and they are often channeled through a cultural lens.
Furthermore, your claim that most people claiming experience of Jesus are the beneficiaries of unsought encounters from above strikes me as being unfair to those that are left out. A loving God would not pick and choose whom to gift an encounter, the experience would be gifted to all without this arbitrary discrimination.