The Legend of Zelda

Absolute classic that influenced game design in more ways than people give it credit for. Including cool secrets in games wasn't really a thing game developers did before this, and it may not seem like it now but back then that was revolutionary. For an NES title, this game was extremely ambitious in scope and gameplay variety. It still holds up reasonably well today, but there is absolutely no handholding so good luck finding some of the secrets without the internet.