Dragon Warrior — Free With Nintendo Power, First in Our Hearts
The RPG Nintendo gave away — and that hooked a generation.
For a huge number of American kids, Dragon Warrior (1989 here; Dragon Quest in Japan) was the first RPG they ever played, because Nintendo literally gave it away free to Nintendo Power subscribers to seed the genre in the West.
It's slow by modern standards: one hero, one enemy at a time, lots of grinding levels in the fields outside Tantegel Castle. But it taught a generation the loop (fight, gain levels, buy better gear, push a little farther) and the joy of finally being strong enough to face the Dragonlord.
It walked so Final Fantasy could run. A foundational cartridge, and a clever giveaway that paid off for decades.