Similar games are R-Type, Silpheed, Phalanx, Darius, In the Hunt, Z-Out, Einhander, and Katakis. Over the years, the Gradius series has spawned a decent amount of sequels. The original Gradius was released in 1985. In the Gradius saga, you pilot the most advanced starship known as the Vic Viper. This series has always put you up against hulking, difficult bosses and in the PS2 installment, Gradius 5, the developers went over board and decided to take Gradius to a whole new level of intense action. Konami has also made a parody series on Gradius known as Parodius.
Salamander ('Life Force' in the U.S.)
Gradius III & IV Re-release