I like Xevious and Zaxxon. Zaxxon was cool because it had a unique isometric perspective that I haven’t seen in another game.

Gradius 3 specifically I found to be quite fun. Its too bad Konami retired the Gradius series, but I suppose its probably better that way.

The Panzer Dragoon series is a great arcade shooter series.

Contra. Contra 4 specifically on the Nintendo DS I felt had the perfect balance. I really liked that entry.