Cornerstone games are pretty much a different thing for everyone. Here are mine
NES - Mario, Zelda, Mega man, Metroid, Dragon warrior, Final fantasy
SNES - Final fantasy, Chrono Trigger, Zelda LTTP, Super metroid
N64 - Who cares, the system is the worst one ever released
SMS - Alex Kidd, Phantasy star
Genesis - Golden Axe, Phantasy star
Dreamcast - Dont think I could list a single DC game if I tried
Saturn - Magic Knight Rayearth, Albert Odyssey
Sega CD - Lunar 1&2, Vay, Popful Mail
PS1 - Final fantasy series, Chrono Cross, Dragon warrior
PS2 - Baldur's gate
PS3 - God of War!
Xbox - Dungeons and Dragons heroes ... Im sure people would name the Halo type games too but those suck!
Xbox 360 - Refer to Dreamcast
Gameboy(s) - Tetris, Final fantasy adventure/legends, Zelda Oracle games, Dragon warrior monster games
DS - Final fantasy 3, 4 heroes of light, Y's remakes, Radiant historia