The NES, SNES, Atari 2600 and G7000 (Odyssey2) were already in the family's possession, so I didn't have a part in that. For Nintendo consoles, it usually only takes one game, for non-Nintendo consoles, it's more. Sometimes, a certain feature was a great incentive to get a console. Only the N64, Dreamcast and WiiU were bought on launch-day.
Mega Drive: Sonic the Hedgehog, Mortal Kombat
N64: Super Mario 64
PlayStation: Crash Bandicoot 2, CD-based
Dreamcast: SoulCalibur
GameCube: Luigi's Mansion, price-cut
PlayStation 3: Uncharted, Motorstorm, blu-ray, HD
Wii: Wii Sports (not at launch due to low stock, had Twilight Princess on GC already, got Wii version later)
WiiU: NintendoLand, ZombiU, Gamepad
GB: Super Mario Land, Tetris
GBpocket: Pokémon Blue, form-factor
GBcolor: The Legend of Zelda: Link's Awakening DX
GBA: Yoshi's Island: Super Mario Advance 3
DSlite: Mario Kart DS
3DS: The Legend of Zelda: Ocarina of Time 3D