Theres a huge misunderstanding of what makes a song famous here. People are essentially herd animals are extremely impressionable.
Songs become famous because they are marketed, and it has nothing to do with the quality of the song.
I cant answer what makes music good, as it's a personal thing. I can tell you how good music affects me. Generally there is some form of development or repetition.
What makes notes fit after others?
Convention, particularly regarding their relativity to the tonal centre of the piece/section. If a note is within a chord, or a mode that applies to a chord it generally fits quite well. Generally speaking, leading tones (7ths) resolve to the one, and subdominants (4ths) resolve to dominants (5th) if suspended, otherwise they can also resolve to the tonic (1)
Typical progressions for melody (in terms of resolution) are embellishments on 2-1, 3-2-1, 4-5-1, 5-1 (from above or below), 6-5-1 (from below), 7-1 (from below).
When you venture into jazz you get some things in reverse since its around the cycle of 4ths rather than fifths, so 2-5-1 etc. 7-1, etc still apply of course.
A lot of it had to do with what we are conditioned to hear and basic concepts of euphony. In the baroque period, interrupted cadences were rarely used by Bach and were considered cacophonic, however they became very popular and were considered euphonic in the romantic eta. I'd rather not get into the physics about why some things are euphonic and are not. A simple not way of looking at it is that perfect fifths etc are more present in nature (apparently) and seem more "natural".
Q3: How much is music taste affected by family and friends?
Varies from person to person. My music taste is generally influenced by my own curiosity, ear and my education. Other people just listen to stuff because their friends do. That's fine
etc.