What are your top three favorite classical compositions?

1. Beethoven Eroica

2. Bach Goldberg Variations

3. Verdi Lat Traviata

1) The Baroque Period

2) The Classical Period

3) The Romantic Period

Bach Sonatas and Partitas for solo violin

Beethoven Symphony 9

Mahler  Symphony 5

I admire everyone’s good taste!

Not so deep into classical but 3 (even...3) is impossible, i will follow the rules,

Berlioz Symphonie Fantastique

Britten The Young person’s guide to the orchestra

J.S.Bach The concertos for 3 and 4 Harpsichords (BWV 1065, 1064, 1063)

First ones most likely they come from my childhood.

As it appears most folks like orchestral,

 

My list is mostly orchestral, only because those are the pieces that come to mind first.

But truth be told, there are plenty of pieces for chamber ensembles that I rate equally as those in my list above.

Charles Wuorinen - Chamber Concerto for Oboe and 10 Players (1965), Chamber Concerto for Flute and 10 Players (1964)

Elliott Carter - String Quartet No. 3 (1971), and No. 2 (1959), Asko Concerto for sixteen players (2000)

Anna Thorvaldsdottir - Hrim (2010),

Stravinsky - The Soldier’s Tale (1918)

Stefan Wolpe - Chamber Piece No. 1, chamber orchestra (1964)

Magnus Lindberg - Souvenir (2010)

This is exactly why the OP’s request for only 3 pieces is an impossibility.

A great question.  For right now, I'd have to say:

--Beethoven's Ninth Symphony.

--Mahler's Second (Resurrection) Symphony

--Mozart's Don Giovanni

Another three off the bottom of my head --

Mahler's Wunderhorn songs.

Stravinsky's Petrushka

Puccini's Turandot.

As it appears most folks like orchestral, a few that are heard more often in my house - Sibelius Sym #4 (and his Finlandia Hymn, original version, by male choir, highly recommended for those who feast on nationalistic music), Last movement of Mahler's #2, all of Mahler #6, Prokofiev's Piano Concerto #3.

Schubert Symphony 9 

Beethoven Violin Sonata No. 5

Mahler Symphony 9

Vivaldi The Four Seasons

Beethoven 5th Symphony 

Handel Messiah 

What the heck. I'll give it a go. Off the bottom of my head --

Prokofiev's Piano Concerto No. 3.

Beethoven's Sixth Symph,

Tchaik's Fifth Sim.

Poulenc PR 61.

@tablejockey 

I like how on the album cover it seems to very casually mention “…and symphony No. 8….” in small type, like it was just a throw-away done by Beethoven. 🤣

I'm not "seasoned" enough as a Classical listener (only 20 years or so) to have definitive faves yet..

I Do however agree with my go to FM stations 2022 #1 pick

Ludwig V's 9th.

The Classical California Ultimate Playlist Returns | See What Made The List - Classical KUSC

Perhaps a generic/vanilla pick for discerning Classical afficionados, but the history/story behind the piece and Ludwig V's debut performance left me intrigued and a fan since learning about it.

The 2nd movement played VERY loud of my pristine 1959 RCA Living Stereo press never fails to catch my attention.

Of the countless interpretations of this masterpiece, this one is my favorite. Strongly recommended for anyone building a Classical collection with "Golden Age" Living Stereo LP's.

Cheap, probably "better" than most reissue or audiophool  copies.

You’re right!  
Three is a near impossible task. And, as was said, it might be different tomorrow. 
 But, here goes:

 Mahler 9th Symphony 

Mozart Requiem

Almost any Mozart Piano Concerto (cheating)

Out of thousands, you jest! But I do seem to listen more often to solo piano music by Chopin, Debussy, Beethoven, Brahms, Schubert, Schumann, and Prokofiev than most others. 

How about you?

Bach Goldberg variations, Elgar enigma variations, Beethoven’s seventh Symphony

Three!? Seriously!

I could never narrow it down to just three, even 10 wouldn't be able to cover all the classical music I rate equally highly. So, I will have to cheat. 😉

I am only into: 20th century, atonal, serial, avant-garde classical music. Mostly from post 1950 to the present.

Alban Berg - Violin Concerto 

Elliott Carter - Concerto for Orchestra 

Charles Wuorinen  - 4th piano Concerto 

Joan Tower  - Concerto for Orchestra 

Ernst Krenek - Static and Ecstatic 

Magnus Lindberg  - Sculpture

And a few, less 'thorny' sounding pieces:

Bartok - Music for strings, percussion, celesta

Samuel Barber - Piano Concerto 

Stravinsky - The Rite of Spring 

Again, there are many other pieces that I rate as highly as those I listed. If I made this list tomorrow, it could be almost completely different.