What is the best Nocturne by Chopin?

There is no best. You listen to his nocturnes and decide which one or ones you like best. It's a matter of individual taste. There is no one composition that's the most beautiful I've ever heard. I'm a music lover and enjoy numerous beautiful compositions of various genres.

I don't understand why people ask these "best" questions about music. What could be a more absurd inappropriate type of question? 

Top nocturnes by Chopin, ranked

1. C♯ minor Op.27 No.1

https://www.youtube.com/watch?v=QAcAWWU_0mE

2. C minor Op.48 No.1 

3. G major Op.37 No.2 

4. B♭ minor Op.9 No.1

5. G minor Op.15 No.3

6. E♭ major Op.9 No.2

7. F♯ major Op.15 No.2

For this list, I excluded 3 of the nocturnes from consideration because I don't have a firm opinion on them yet. Those are two from Op.62, B major and E major, and Op.60 Barcarolle (it's quite a nocturne despite its name).

No.6 and 7 are listed because of their popularity. They are not higher because: 

- E♭ major is graceful but shallow and naive, the same league as Beethoven's Für Elise and it should be played like that, without affectation.

- F♯ major is nice but ornamented to the edge of kitschy, it seems to me like something written for Liberace.

That was not what he asked for...

Best nocturne by Chopin?  Not sure.  I'm more of a casual fan of concert (do NOT call it "classical") music.

The most beautiful piece of concert music I've ever heard what when I went to see the Pittsburgh Symphony (conducted by Lorin Maazel) perform Beethoven's 9th Symphony.  The final movement, the "Ode to Joy" movement, is simply glorious.

This version is really cool, too.

https://www.youtube.com/watch?v=a23945btJYw&t=21s

I haven't listened to all of any of the popular classical composers work but while at CUNY and working with FL Studios piano roll for awhile and having to go over music notes again I grasp not only making your own virtual instrument sounds way better but classical music can be anything, any genre and is structured just like drums except way more complex. Almost like a cool looking simple cartoon vs an intricate city scene. All classical music really is layered long melodies. That can speed up or slow down however when input as midi this can be input via two methods. I don't write sheet music well enough to know if that is the same as writing because different DAWs and midi sequencers use different terms for almost everything. Like a step in FL Studio is a 16th note. Another thing is the scales don't actually matter at all depending on the instrument you use. They are actually better as a starting point with classical instruments but the overall structure of a comp and instrument selection matters most as far as something sounding good. One example why is that you can use a wave table synth with 2 or 3 oscillators and adjust the settings, change the pitches by semitones, and apply multiple filters and in the end a C4 or C5 on a piano is not the same note as with this synth. Another good example is just playing with the bass synth presets on various synths you will notice what I am saying. I'm sure this is similar between instruments like Banjos, Pianos, vs Japanese or other countries instruments but synths are a more notice in note difference adjustment neccesity between instruments. Basically playing Beethoven on a Grand vs Harpsichord will sound like the same price.