These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Adaptation Displacement: The original version was released in 1985. The world-famous Game Boy version was released four years later.
A lot of players also love the I block because it's usually used to fill a gap that will result in getting a tetris (clearing four lines at once).
First Installment Wins: Any time someone brings up Tetris, the Game Boy and NES versions almost always come to mind. Subverted at the same time, in that these aren't the original versions; the first version of Tetris was released on an Elektronika-60 computer in 1985.
The I block has it, too, mostly because it's the only one that can get a Tetris.
That One Level: The Crystal Tower levels from the Hide n' Seek mode in Tetrisphere, which appear rarely, only in later chapters, and always as the last level before an actual Hide n' Seek level. In Tower levels, you have to expose a picture at the bottom of the tower by moving and destroying the blocks covering it. Crystal Tower is the same, but destroying a block next to any part of the tower (or carelessly moving a block into it) also destroys that piece of the tower, which is an instant Game Over in a game that gives you three lives per level. This means any chain reaction that makes its way to the tower is an instant fail, even if it happens under the layer of blocks you're looking at.
The infinite spin mechanic, which some players feel makes high scoring runs trivial.
In Tetris Friends Marathon mode, a 15-level score attack mode, the scoring system is particularly biased against Tetrises. To be a little more specific, doing 2-combos of singles and T-Spins yields more points per Goal unit than a Tetris, which takes off 8 units and therefore causes the game to end sooner.
What Do You Mean, It's Not Political?: It's been argued that the game is a metaphor for life in the Soviet Union. The "Complete History of the Soviet Union" song plays this angle for all it's worth.