Classical music newbie needs your suggestions

Schubert’s C major string quintet may well be the most powerful, absorbing, ..., piece of chamber music ever published.  It is tops on my desert island list.

I admire your quest. This forum may be a bit overwhelming, as most people are listing their personal favorites which you may or may not connect with. 
 As somebody has suggested, you might take a Music 101 or adult education music class to get you started. A good teacher will inspire you with his or her enthusiasm, and guide you on a path of well known classics that have connected to many beginners.

@thomas_vick 

Funny you should such disparate pianists as Horowitz and Gould in the same article. Usually not paired, they’re my two favorite pianists in the world.

You are in for a musical experience  you never dreamed of - especially when listening on a good sound system!  I strongly recommend that you sample the extensive classical selections on YouTube,. The sound quality is surprisingly good with a quality headphone pair, and you will discover many vintage recordings from the golden era of classical stereo. There will be occasional annoying commercials - but the quality and variety of the music is fascinating.

Of particular interest are live recordings posted from Germany and Japan by the YouTube classical community, usually supplemented by worthwhile comments.  I have been particularly impressed with the performances by Charles Munch and the Boston Symphony of works from the French repertoire.  Also noteworthy are the amazing live performances of the Bruckner 7th and 9th Symphonies by Sergiu Celibidache and the Münchner Philharmoniker. Happy listening; your musical adventure is just beginning.

Dear rvpiano, Horowitz and Gould are definitely my two favorite pianist of all time along with Martha Argerich and Rubenstein who played Chopin like no other.