Classical music is music that was (is) written to be played a specific way with specific orchestrations -- be they quartets, full orchestras, solo instruments (piano, organ, guitar), singers or any combination thereof. In its broadest sense it was written from the eras of Bach to Ligeti, but strictly speaking involves the period of Mozart, Haydn and early Beethoven. Forms include symphonies, concert overtures, concertos, operas and many others. I find it odd that when the phrase "Classical Music" is used most people never realize just how multi-faceted and encompassing the genre actually is. (A good many film composers were excellent classical composers in their own right -- B. Herrmann, S. Prokofiev, M. Rosza, J. Williams, just to name a few, and their styles of composition carried over to the screen.) The music from the film Psycho was written in the most strict classical forms, as too was North by Northwest -- their soundtracks play like symphonic tone poems. Most people would probably not realize that a good amount of music they recognize is in fact Classical Music ... composers like Franz List and Rossini quickly come to mind.
So, why do many people poo poo it? Personally, I think it's because so many don't understand or even know much about it ... and that's not meant to be insulting, just an observation. How many can name a composer for every letter of the alphabet? -- Albeniz, Brahms, Chopin, Dvorak ... etc., and then give a work by each? Wow, that's a lot, eh? -- doesn't even scratch the surface! You could listen to days (if not weeks) of music by each one, that's how much there is to explore. And then do the whole alphabet over again with different composers. And then you would be surprised as to how much of that music is incorporated into today's popular music -- and how much of yesterday's popular (folk) music was used by classical composers -- listen to Dvorak's New World Symphony as an example.
There's so much out there it's almost impossible not to like some aspect of it -- and chances are, you already do.
Classical Music that is easily liked ...
F. J. Haydn -- Trumpet Concerto in E flat major.
R. Strauss -- Till Eulenspiegel's Merry Pranks.
I. Stravinsky -- Symphony No. 1.
M. Moszkowski -- Concerto for Piano.
A. Bruckner -- Symphony no. 4 (Romantic)