Cheating doesn't count when you're talking about a game's difficulty.
Anyway, the Konami code also worked for Gradius, Kid Clown, Tengen Tetris, Nemesis, TMNT: Fall of the Foot Clan, Raging Fighter, TMNT: Turtles in Time, Zombie Nation, and Top Gun 2; modified or backward versions were in Gradius 3, TMNT 3, Batman Returns, Final Fight 2, Gyruss, Mortal Kombat 3, NBA Give-N-Go, North and South, Operation C, and Smart Ball.