"M", "Endless sorrow", "CAROLS" and "STEP you" are first that come to mind. Other than those, "INSPIRE", "my name's WOMEN" and surprisingly "Bold & Delicious" would also fit in as personal classics.

A Song For XX
RAINBOW
M
evolution
SEASONS
Dearest
HEAVEN

These are what I consider to be her classics. and just because I consider these as her classics, it doesn't mean I like these songs.

i would agree with ayus universal classics. i dont have my own classics much because i was only fan since GUILTY era.

but some songs that have that feel to me like oh this is (or is going to be) classic.

i do have a new personal classic:

+

no way to say
voyage
Endless Sorrow
RAINBOW

come to mind, for me. Seeing as the first two won Record of the Year, I think they should be classics damn it! Endless sorrow was one of the first songs by Ayu I really loved and it's almost a decade old now, and RAINBOW is just RAINBOW, I dunno, it's classic for me.

They all give a very vintage Ayu feel for me.

The real classics are the ones she always sings at concerts, like evolution, boys & girls and some of the first few that come to mind. I consider both of those super classic, mind the term, because they're the ones I remembered the most from even before I became an Ayu fan.

There's also Dearest, M, Trauma, HANABI etc a lot of her older songs.

A newer classic I agree is MY ALL, though I don't personally see it as one...it having its own dance and being performed at the end of concerts signifies it may become a new classic.

My personal list: monochrome, SURREAL, RAINBOW, Memorial Address, Ourselves, Moments,teddy bear, Key~eternal tie version~, I am..., still alone, alterna, (miss) understood, until that day... andI could go on and on~these few are the ones with my favourite lyrics though~

I don't understand this topic too.
I have to choose the songs I'm never tired to listen ?
Hmmm...

About you
alterna
Born to be...
kanariya [pv version]
starting over (okay, is an interlude, but I listen every time)
Trauma
M (Above and Beyond remix)

I think more recently, the Ayu hits I would regard as classics are:

BLUE BIRD
Days
Sunrise ~LOVE is ALL~
RED LINE ~for TA~
MY ALL

HEARTPLACE
POWDER SNOW
OVER
END OF THE WORLD

and more,but now i forget xD

Carols is still my fav ayu song...

HEAVEN
Trauma
A Song for XX
evolution
M
SEASONS
Dearest
fairyland
STEP you
Moments
Memorial Adress
teddy bear

And newer classics would be: Mirrorcle World, days, Microphone, Sparkle and You Were...

For me, Trauma for sure. First song and first performance I've ever seen.

And the songs in A BEST2 white. First album I bought. So nostalgic (for me!)

My first Ayu songs:
GAME
INSPIRE
Replace
Boys & Girls
fairyland

Songs which I've loved at first listen, love and will love forever:
Pride
forgiveness
SURREAL
Duty
End of the World
Key ~eternal tie ver.~
Real me
Free & Easy

Ayu classics are also classics to me:
A Song for xx
Trauma
evolution
AUDIENCE
SEASONS
Who...
M
UNITE!
Dearest
independent
Voyage
RAINBOW
Memorial address