Ah yes. Tetris,
the second highest selling game of all time (and the highest selling game for
decades before Minecraft just recently took the top spot), is
not at all memorable or deeply embedded into popular culture as we know it. Puyo Puyo, a series that is just now seeing a reboot in Japan and only just now getting off the ground in the West is
far more memorable and deserving of a spot in Smash. These are
totally objective criteria of a series' popularity and
not at all something I've made up on the spot to justify my own confirmation bias.
There are definitely arguments for Puyo Puyo over Tetris,
but this ain't it chief.