ALttP hands down. Though AoL was my first Zelda game, its a lil intimidating to be returning too time and time again. I would have to say I play through ALttP every 6 months. I know the game like the back of my hand, and can beat it in just two settings. The first three dungeons only take about an hour for me to complete give or take about 15 mins. So i usually make it around three dungeons into the dark world on my first setting. Then I come back the next day and do nothing but wander around collecting things, and heading to the entrance of the next dungeon, before deciding to save it for the next sitting. So i guess three settings is more likely.
The game is bursting full of content, with secrets, and goodies in every nook and cranny of the world. I love the 16-bit era of music. Darkworld theme being probably my most beloved music in all of video games (along with tons of MegaMan/MegaManX music). How ever I would be wrong to not give a ton of credit to nostalgia.