I remember this game extremely fondly, although the version I had was called Power Strike, for the Sega Master System. I'd highly recommend it... but be warned, it's bloody hard! Yet I did manage to beat it twice as I recall; I was so proud!
(screenies and a review can be seen here: http://www.classicgaming.com/reviews/sms/pstrike.htm
There was sequel, Power Strike II for the Master System, but I'm not sure if it was unique to that system or not. I must play it properly some day!
I also agree with R-Type being an all-time Classic. I think Nemesis/Gradius (along with it's sequels) should be included too. Space Harrier simply because it seemed so revolutionary at the time... and still appears unique, in looks at least, today. But my all-time favourite shmup would be Choplifter (Arcade), simply because I grew so attached to the little fellows you had to rescue... it was so enormously satisfying to dodge down past the AA guns, and pick up the peeps... it's Defender. But with Helicopters. And based on an old Apple game, fact fans...