There is just no way I can narrow it down to a top 3. There was a LOT of great ost this gen (don't forget about the indies)
Just a quick glimpse of what I have on my iPhone only (or what I intent to buy) :
A Plague Tale : Innocence
Alien Isolation
Animal Crossing
Another Eden
Atelier Ryza
Assassin's Creed Odyssey
Assassin's Creed Origins
Bayonetta 2
Below
Bloodborne
Celeste
Concrete Genie
Control
Death Stranding
Detroit Become Human
Disco Elysium
Donut County
Doom 2016
Dreams
Dying Light
Ether One
Everybody's Gone To The Rapture
Fallout 76 & Wastelanders
Far Cry 5
Far Cry New Dawn
Farlands
Fat Chicken
Final Fantasy XIV
Final Fantasy XV
Final Fantasy 7 Remake
Final Fantasy 8 (yeah?)
Firewatch
Florence
Furi
Gears Of War 4&5
God Of War
Gone Home
Gravity Rush 2
Gris
Gungirl 2
Halo 4&5
Horizon Zero Dawn & Frozen Wild
Hotline Miam 1&2
Interstellaria
Klang
Kona
Last Day Of June
Life Is Strange Before The Storm
Life Is Strange 2
Little Nightmares 1&2
Longshot + Longshot Homecoming
Mafia 3
Medievil PS4
Metro Last Light
Mirror's Edge Catalyst
Nier Automata
Ni No Kuni 2
Octopath Traveler
Ori 1&2
Oure
Outer Wilds
Persona 5
Poly Bridge
Prey
Pyre
Red Dead Redemption 2
Resident Evil 2 Remake
Resident Evil 3 Remake
Resident Evil 7
Shadow Tactics
Shape Of The World
Shatter
Soma
Stardew Valley
Subnautica
Super Mario Odyssey
The Evil Within 2
The First Tree
The Legend Of Zelda : BotW
The Legend Of Zelda : Link's Awakening
The Order
The Vanishing Of Evan Carter
The Walking Dead
The Witcher 3
The Wolf Among Us
Tom Clancy Ghost Recon Wildlands
Tomb Raider : Shadow Of The Tomb Raider
Transistor
Uncharted 4
Uncharted Lost Legacy
Wolfenstein 2
Xenoblade 2
Yoshi's Wolly World
Ys VIII
Still waiting on :
The Last Of Us Part 2
Ghost Of Tsushima
Cyberpunk 2077
Dying Light 2
Some might not be 8th gen... I know ost more than games, sometimes...
I'm sure I'm forgetting some, too...