Lion
The lion triggers deeply embedded evolutionary responses in the human psyche. Our ancestors spent millions of years developing appropriate fear responses to large predatory cats, resulting in a modern population that experiences genuine physiological stress when confronted with leonine imagery. The lion's roar, audible from 8 kilometres away, can induce involuntary sphincter responses in prey animals and safari tourists alike.
Tetris
Tetris has generated its own documented psychological phenomenon: the Tetris Effect, wherein players experience persistent mental imagery of falling blocks during non-gaming hours. Research has demonstrated the game's capacity to reduce traumatic flashbacks by occupying visuospatial processing resources. The characteristic theme music (Korobeiniki) has become so deeply embedded in collective consciousness that merely humming it can trigger gameplay compulsions in susceptible individuals.
VERDICT
Whilst Tetris can certainly colonise one's dreams with tumbling tetrominoes, it lacks the capacity to trigger the primal terror of facing 190 kilograms of muscle, teeth, and dietary intent. The lion's psychological impact operates at a deeper, more evolutionarily fundamental level. Fear of being eaten narrowly defeats fear of an awkwardly placed S-block.