He seems like a nice decent guy. It sounds like it is hard for you to admit to him that you are not physically/romantically attracted to him. I can see that perhaps because he is nice you don't want to hurt his feelings. I don't know what your background is with past relationships or what type of person you are normally attracted to. Sometimes a person is fantastic but you just don't feel that special chemistry with them and so they become a friend. It is ok to tell him that you are not attracted to him in that way and that you wanted to be attracted to him but instead you feel close to him more like a friend. He may not like to know that at first but it is better in the end because it allows him to find someone who feels a mutual attraction with him.