I love a good Zelda thread :)
1) Ocarina of Time -- I consider this the best game ever made, so it wins this contest fairly easily. The dungeon and world design is spectacular; the music and sound design unrivaled; and the sense of wonder and discovery exceptional.
2) A Link to the Past -- The quintessential Zelda game, A Link to the Past codified what modern games know and love about the series. Mechanically and graphically, the game shines. Its boss battles and secrets are legendary. Its pacing and reward structure immensely satisfying.
3) Majora's Mask -- The strangest and boldest of the series, Majora's Mask is a love-it-or-leave it affair. Personally, I adore it. The 72-hour timeline hook is a brilliant gameplay device, and its side quests are among the best in any game, ever.
4) A Link Between Worlds -- What seems on the surface like a carbon copy of A Link to the Past is in fact an independent and surprisingly refreshing take on the Zelda franchise. The visuals pop thanks to the 3D effect on the 3DS; the amount of content is huge, both offline and online (thanks to StreetPass); and the painting mechanic is deployed to great effect throughout the game.
5) The Wind Waker -- Originally criticized for its cartoon appearance, The Wind Waker has now become a fan favorite. And for good reason. It boasts some terrific music, a surprising story line, and a huge, open world ready to be explored.