There's a high number of known games and of high scores (from "professional" reviews, or from general consensus being well appreciated) that I've never actually played, that's for sure. I can name a good bunch by heart easily, note however that I've actually seen most of them in action, either on YouTube or watching someone play it without playing it myself.
I checked the scoring list of GameSpot and sorted it by scores from highest to lowest, and I went through the list to see which ones I clearly remember I've never played myself. I haven't picked all of them, otherwise it would take me too much time and I'm not at home right now as I type this, so here goes for me:
Metroid Prime [Series] (GC)
Super Mario Galaxy 1 & 2 (Wii)
Jet Grind Radio (DC)
Xenogears (PS1)
Seven Kingdoms (PC)
Star Control 3 (PC)
Resident Evil 4 (GC)
Resident Evil Code: Veronica (DC)
Resident Evil Code: Veronica X (PS2)
Uncharted [Series] (PS3)
Gears of War [Series] (X360)
Metal Gear Solid 3: Subsistence (PS2)
Metal Gear Solid 4: Guns of the Patriots (PS3)
Chrono Cross (PS1)
Vagrant Story (PS1)
The Longest Journey (PC)
Dark Souls (X360/PS3)
Red Dead Redemption (X360/PS3)
God of War [Series] (PS2/PS3)
Skies of Arcadia (DC)
Grandia (PS1)
Panzer Dragoon Saga (Saturn)
Wizardry 8 (PC)
L.A. Noire (PC/X360/PS3)
Assassin's Creed 1 & 2 (X360/PS3)
Dead Space 1 & 2 (PC/PS3)
And many others, over the years, and across all the platforms I've owned. I know I haven't played a crap load of "best" or "known" games, unfortunately one life time wouldn't be enough to play them all (I wish I could really).