This is a revised post from my previous one, however long ago it was posted. (Probably a couple months.) I've figured out why my least-favorite Zelda is my least-favorite Zelda over this course of time, so I figured I'd delete my previous post and post this.
A Link to the Past. Don't get me wrong, the game is fantastic and I do like it, but every time I play it, I find myself having to force myself to play after about an hour. It really bugs me, as I had a blast the first time I played it -- I actually had a hard time putting it down. But now... not so much. This is probably due to the fact that it was my first time playing it, so I didn't know what to expect out of the story. Now that I do, the lack of story in it is a major problem for me. (But I'm getting ahead of myself.)
The art style also definitely plays a factor, as the colors are ultra-dull and almost depressing in my opinion. Even Twilight Princess has better colors than this game. (Ironic that I say that, as I quite like TP's art style.)
I think the main reason it's my least-favorite, though, is because the overworld is so large that the content is way too spread out, weakening the vast amount of secrets in the process. The difficulty is also way too cheap, as the simplest of enemies can wind up taking off two hearts, and with enemies around every turn and in every corner, this takes an unnecessary toll. I tend to try to avoid them rather than fight them, which is something I can't say I do in any other Zelda title, even Zelda II.
The game is also too open, relying way too much on the exploration, which is only worsened by the content being spread out so far. This also causes its rather excellent story to be spread thin and feel almost non-existent. I know it's on the SNES, so I have to give it a little leeway in that category, but the game still could have been a little less non-linear.
Some of the dungeons also feel lacking in substance, as if the puzzles act more as obstacles rather than entertaining moments that require brain-power. Again, it's on the SNES, as well as an early game in the series, so some leeway has to be given here, but it's not overlookable by any means. I think the game being less non-linear could have helped with this, as more dungeons would have required certain items from previous dungeons, allowing the puzzles to have more substance.
I can't say I have a complaint with the bosses, though. At least for the most part. Those guys were just fantastic, some of the better ones in the series in my opinion. They don't use that repetitive "hit weak point/stun boss, hack and slash, repeat" style that modern Zelda titles (until Skyward Sword) have used. They're good old-fashioned fights, which is how they should be. That and the music are about the only things I don't have issues with.
Despite all my complaints, I do consider ALttP one of the series' stronger titles -- it's #6 on the list of the best Zeldas in my book -- and I'd probably give it anywhere from a 9.5 to a 9.8 out of 10. The issues I mentioned just drag my overall enjoyment of the game, causing it to be the lowest on my list of favorites.