The Legend of Zelda: Link's Awakening as guessed by BraLoD
High up in the list we find the highest placed handheld game, 'The Legend of Zelda: Link's Awakening'. It's a brilliant game, more than worthy of the title "best handheld game ever made", yet sadly often overlooked. The original release on the GameBoy is already sufficient for a place this high in the list, but the 'DX' version on the GameBoy Color a couple years later, sollidifies the claim.
It is a very original game for the 'Legend of Zelda' series, where Link, the same incarnation of Link as the one in 'A Link to the Past' and the newer 'Oracle' games, is shipwrecked during a storm at sea and finds himself on an unknown island populated by people and talking animals, as well as strange foes. As the story goes on, and not even just for a Nintendo game is this one very story-heavy, hints and events allude to a greater mystery that surrounds the island.
This game still amazes me. It is a GameBoy game, but it is one seemingly impossible to have existed on the system. It runs circles around it's "big" console brother released a year earlier in every way, it even has cutscenes, and I am not at all bummed by the fact that I have bought this game four times on three different devices. What's also mostly unknown however is that this game actually pioneered much of the series' mainstays. Mini-bosses, bosses with multiple radically different stages, a guide-character, musical instruments with different songs for different gameplay purposes, fishing, the trading- and the collect-a-thon sidequests all started with this game. A truly amazing game.