On the 8-bit platforms, the 3D action adventures (as they were
called; the 3D refers to the isometric view
that was generally used) were quite popular. They neither fit the
concepts we nowadays connect with action, nor did they have much
resemblance with classic adventure games. They combined exploration,
collecting things, avoiding more often than fighting monsters or
other dangers, and most of all solving puzzles. A typical example
is Magnetik Tank.
When the 16-bit platforms came, this genre declined, maybe because of the popularity of scrolling games on these platforms. But then suddenly the genre had a comeback, not in the least because of one game: Treasure Trap.
The story is simple: In 1856, the S.S. Esmeralda sank with 20 million Dollar worth of gold bullion aboard. Now it's 1929, you are expert diver Howard Kelp, and you decide to make your fortune by lifting what has rested 300' below the surface for decades. Of course, it is not easy. You have to find the keys for the doors and avoid voracious sharks, electric eels, and other animals as well as traps, all the while keeping an eye on your air supply (which can be increased by finding oxygen tanks).
While the concept is sound, the graphics pleasant and not without humor, I found the game not all that enjoyable because of awkward controls. There is a reason that isometric games became dominant once mice became common. But I guess it just takes some getting used to.
But regardless of the playability nearly two decades later, the game has its place in history. The revived action-adventure was here to stay. More often than not it tended to be in a medieval or fantasy setting, combat replaced the mere avoiding of enemies, and inventory and equipment got more important. Cadaver and The Immortal are examples. The end product of this development is Diablo, and it would, again, start a new era.