Nethack

A great RPG from Origin Systems and quite often overlooked. Top down style from creator Chuck Chuckles Bueche. Post apocalyptic, you play the part in aiding the underground to free the people from enslavement by an evil robotic race known as the Tzorg.

In this conversion from the Amiga RPG, you play the role of four heroes whose mission is to save their world, Kalynthia. It gives you much freedom: there's more to do that just stick to the main quest. Also, while the game is 2D, most of the time, dungeon crawling takes place in a 3D view

Akalabeth was one of the first computer role-playing games and is the precursor to the Ultima Series. Once, the land of Akalabeth was peaceful and quiet. But then came Mondain, an evil and ambitious man who created dungeons and populated them with foul creatures. The noble warrior British was able to drive Mondain from Akalabeth, but the monsters he brought with him remain. As either a fighter or a mage, it is your job to explore Akalabeth, descend into the dungeons and vanquish the beasts dwelling within. On an overhead map of the land, one can find the dungeons, towns where one may buy supplies, weapons and armor, and a castle, where one will be given quests by Lord British. To fulfill such a quest, a certain type of creature must be destroyed in a dungeon. Inside the dungeons, the view switches to a first-person perspective. Fight, explore and find treasure on your way to complete a quest. Each successive quest will require you to destroy a stronger monster, which will reside on a deeper dungeon level than the one before it.