Whether you started with a 2600 and a joystick in your hand, an N64 with a blistered palm or building your first PC in your teens, what is that one video game you've played at some point that to this day sits at the top of your list.
I don't think I've played a game more than FF7 (well, Warhammer 40K Dark Crusade might have it beaten by now, not sure, along with the original Star Wars Battlefront games as a distant third), some things I did:
Omnislash on the first CD
Mastered all the Huge Materia until they split to new ones
Bred my golden chocobos until I had a superfast one that effortlessly won every race with a huge margin
Had a save where everyone was level 99 despite not needing it
Defeated all the Weapons of course
I feel I did even more things but it's been like 20 years, don't remember more...