Tetris

Tetris is an abstract puzzle game released by Alexey Pajitnov in 1985. Tetris enjoyed a great deal of success with many demographics, across multiple platforms.

This game is usually categorized as part of the “puzzle” genre of games. Ironically, it behaves quite different than a puzzle – a puzzle has only one solution, but there is a host of different strategies and play styles.

The core mechanics of the game are absolutely simple, including only 7 piece types. The player maneuvers falling blocks by moving them left or right, or rotating them. The goal is to make horizontal sections without gaps (which disappear) while avoiding having the pieces reach the top of the screen.

There are only a few rules for this game, but the strategies for the game can very greatly from player to player. Some players will leave a groove missing in the accumulating structure in an attempt to fill them all at once to earn more points, whereas a conservative player may try to make lines disappear as quickly as possible.

Tetris was created 23 years ago (at the time of this article), but the original design has a completeness to it that leaves little that could be added to. The game would not be significantly improved with power-ups, more shape variety, or story. Adding anything more to the design would risk throwing the elegant simplicity off balance.

The experience of playing Tetris would not translate into other media. The experience can be so intense, in fact, that it is known to cause unusual - almost obsessive symptoms in some players - which is described by Wikipedia:

The game can also cause a repetitive stress symptom in that the brain will involuntarily picture tetris combinations even when the player is not playing the game (the Tetris effect), although this can occur with any computer game showcasing repeated images or scenarios.
-from Wikipedia Tetris entry

The Tetris effect is the ability of any activity to which people devote sufficient time and attention to begin to dominate their thoughts, mental images, and dreams. It is named after the video game Tetris…

…People who play Tetris for a long time might then find themselves thinking about ways different shapes in the real world can fit together, such as the boxes on a supermarket shelf or the buildings on a street.[1] In this sense, the Tetris effect is a form of habit.
They might also see images of falling Tetris shapes at the edges of their visual fields or when they close their eyes.[1] In this sense, the Tetris effect is a form of hallucination.
They might also dream about falling Tetris shapes when drifting off to sleep.[2] In this sense, the Tetris effect is a form of hypnagogic imagery.
-from Wikipedia Tetris effect entry

[Wow... I thought it was just me]

In 1985 it was far more common for a game to be created by one person. It is perhaps understandable that many games of that period are stripped down to one or two single game mechanics.
Even today, the most successful games seem to be built from a simple set of mechanics that have been polished to a high degree.