Ok my blood pressure is rising. Gun Frontier and Metal Black are my all time favs, both #1! They both have a great story to tell and the music is outstanding, perfect games. Hisayoshi Ogura (OGR) from Zuntata Taito Sound Team (the heart and soul of Zuntata) once said in an interview that the music is very important because it carries the story and mood of the game and these two games are the perfect examples
G-Darius is another one and so many other Taito stuff...
Trivia: Metal Black should have been Darius III but when development was in progress the theme got darker and darker so they decided to make MB. In fourth stage you see the same blue laser guys as in Darius II. What a trip this game is. It's an experience.
Ah I think you know Border Down? It's the spiritual successor to MB, esentially made by the same guys who left Taito and founded G.Rev. This is a must have.