"Peter and the Wolf" was a childhood favorite of mine ( the old Bernstein NY phil. recording on Columbia Masterworks). "The Moldau" by Smetana followed. My older sister had these records and I had none, so I got to listen only to those they had already at first.
So much music for most to choose from these days. Classical is a hard sell for most. Both my kids have some degree of interest in classical music among others as well I like to think from hearing dear old dad play it all at one point or another, among other things. My daughter is into her third year of playing violin with the Middle School Orchestra and seems to be coming into her own there as well.
Leroy Anderson is where I would recommend for many to start first. So many short, catchy and immediately recognizable contemporary classical compositions there, including stuff you hear every CHristmas.
Many ways to go from there. bach, Mozart, Tchiakovsky, BEethoven, Sibelius, Rachmaninoff, maybe even Mahler and Stravinsky for some classical music with an edge. Hard to say.
Dance music maybe? Strauss waltzes, Czech Marches, Tchaikovsky Ballet music? Sousa marches maybe? More people are probably likely to relate to music that one can dance or perform to.