I would submit that he has accumulated a song and album catalogue minimally equal to Bob Dylan, who won the award previously.
Consider the hit singles (many more than Dylan):
The Sounds of Silence (1964)
I Am a Rock (1965)
Homeward Bound (1966)
The Dangling Conversation (1966)
A Hazy Shade of Winter (1968)
At the Zoo (1968)
Mrs. Robinson (1968)
Fakin’ It (1968)
Bridge Over Troubled Water (1970)
Cecilia (1970)
El Condor Pasa (1970)
The Boxer (1970)
Mother and Child Reunion (1972)
Me and Julio Down by the Schoolyard (1972)
Kodachrome (1973)
Loves Me Like a Rock (1973)
50 Ways to Leave Your Lover (1975)
My Little Town (1975)
Slip Slidin’ Away (1977)
Late in the Evening (1980)
Graceland (1986)
You Can Call Me Al (1986)
Diamonds on the Soles of Her Shoes (1986)
Boy in the Bubble (1986)
The Obvious Child (1988)
Born at the Right Time (1990)
Father and Daughter (2003)
Consider, too, the myriad other memorable songs:
Red Rubber Ball (recorded by The Cyrkle)
Richard Cory
Kathy’s Song
April Come She Will
59th Street Bridge Song
Scarborough Fair/Canticle
America
Old Friends/Bookends
A Most Peculiar Man
American Tune
Under African Skies
and many more from the albums:
Baby Driver, Big Bright Green Pleasure Machine, Cloudy, The Cool, Cool River, Darling Lorraine, Flowers Never Bend with the Rainfall, Getting Ready for Christmas Day, Gone at Last, Gumboots, Homeless, How Can You Live in the Northeast?, Hurricane Eye, One Trick Pony, Patterns, A Poem on the Underground Wall, Punky’s Dilemma, So Beautiful or So What, So Long, Frank Lloyd Wright, Spirit Voices, Still Crazy After All These Years, Take Me to the Mardi Gras, That Was Your Mother, Wartime Prayers, You Don’t Know Where Your Interest Lies, et al.
And the memorable, popular, strong-songed albums:
Wednesday Morning, 3 am (1964), Sounds of Silence (1964),Paul Simon Songbook (1965), Parsley, Sage, Rosemary and Thyme (1966), Bookends (1968), Bridge Over Troubled Water (1970), Graceland (1986), Rhythm of the Saints (1990), You’re the One (2000), Surprise (2006), So Beautiful or So What (2011), Stranger to Stranger (2016).
The best Simon and Garfunkle live concert: The Concert in Central Park.
The best Paul Simon live concert: The Graceland Concert.
And song-lines that often read like poetry:
-The Mississippi Delta was shining like a national guitar
-Homeless, homeless, moonlight sleeping on a midnight bay
-And the people bowed and prayed to the neon god they made
-I have my books and my poetry to protect me
-On a tour of one-night stands, my suitcase and guitar in hand
-It’s a still-life watercolor on a now-late afternoon
-Time, time, time, see what’s become of me
-Zebras are reactionaries, antelopes are missionaries
-Like a bridge over troubled waters, I will lay me down
-Goin’ home, where the New York city winters aren’t a-bleedin’ me
-Mama Pajama rolled out of bed and she ran to the police station
-And furthermore I hope my meaning won’t be lost or misconstrued
-If you’ll be my bodyguard, I can be your long-lost pal
-And the bomb and the baby carriage were wired to the radio
-In restless walks she’ll prowl the night
-Just kickin’ down the cobblestones, lookin’ for fun and feelin’ groovy
-How terribly strange to be seventy
-Wish I was a Kellogg’s cornflake floatin’ in a bowl takin’ movies
-Pattern still remains on the wall where darkness fell
-Toss me a cigarette, I think there’s one in my raincoat