I had Sinistar on a SNES arcade collection as a kid. The game is tense on its own, but if you don't know how to kill Sinistar, the game runs on a whole new level of fear, a sort of existential despair even. You can shoot the ships and rack up points and it's fun and satisfying, but every second, Sinistar comes inexorably closer to completion. And once he's done, your doom is sealed - you can try to evade him for a while, but he'll always catch you in the end. You were doomed the moment you pressed start.

Naturally, it was my favorite of the bunch.