I agree with pretty much everything illmatic said. I definitely think A Link to the Past is the prototypical Zelda and also the best one. The same can be said for Ocarina of Time but OOT is just a simplified version of ALTTP in 3d IMO. If you complain about the difficulty in modern Zeldas than ALTTP is the game for you. The dungeons are true labyrinths in many cases and despite the size of some of the dungeons there is never wasted space. ALTTP is the first game in the series to really take puzzle solving somewhat seriously and as a result the dungeons can be really challenging.
This game is the one of the few games in the series that seems more for hardcore fans than casual fans. What I mean is that the game is fairly challenging all the way through, and there isn't any tutorial as is the norm in the modern games. You gain control of Link and immediately set out to the first dungeon (technically this one may be considered a mini-dungeon).
My favorite aspect of the game in contrast to the modern games of the series is the extreme amount of nonlinear progression that is possible. Once you get to the "middle" of the game you start your true adventure, and you are basically set free after completing the first dungeon in this part of the game. You then have tons of freedom to tackle the dungeons in many different orders, and the order you choose to do them in can benefit you in the long run. For instance I actually was playing through the game yesterday and today and went through the dungeons in the order 1, 4, 3, 6, 5, 2, 7. Doing the 4th dungeon early gives you the opportunity to upgrade your sword sooner and doing the 6th before the 5th lets you solve a puzzle in a much faster way. The dungeons themselves have tons of freedom as well and some have multiple paths through them. For instance most people would play through the game thinking that you need the item from the 2nd dungeon to complete the 5th and 6th dungeons but there are other ways to get through them.