From Wikipedia:
Gradius (グラディウス, Guradiusu, /ˈɡræd.i.əs/ GRAD-ee-əss) is a series of shooter video games, introduced in 1985, developed and published by Konami for a variety of portable, console and arcade platforms. In many games in the series, the player controls a ship known as the Vic Viper.
The arcade version of Gradius was released internationally outside Japan under the title of Nemesis, although subsequent home releases have the original title. There’s also a series called Salamander (Life Force), which is considered as a part of Gradius series, but with slight different game mechanics, such as switching between Side Scroller and Vertical Scroller.
There’s a fanmade font named Gradius that’s based on the logo itself. But the actual logo used Langdon Biform, with modified G and S and also using 1 for the I letter.
“Destroy the Core!” is the most memorable quotes when player facing the boss battle of the games.