8 bit
16 bit
32 bit
post 32 bit
I always hear about the 16 bit era as being the "golden age" of shmups by a lot of mainstream reviewers. Which I don't agree with.
For me, shmups started to peak around the middle or end of the 16 bit era, with games like Thunder Force IV and R-Type III. But really peaked around 95-99, with the 32- bit systems and arcade scene. All of Cave's best stuff was from this time, so was Raizing's. Then you had stuff like Eihander, G- Darius, R-Type Delta, Layer Section, Radiant Silvergun, and Gradius Gaiden just rounding out the awesomeness. And I know i'll get greif from Psikyo fans for not adding them in there, but if you like them, just tack them on to that list.

This for me was truly the golden age of shmups. After that, it's been kinda hit and miss. We've had some absolute classics with Ikaruga and Gradius V. And there's been other good games, but nothing that has really wowed me, besides Treasure's stuff.
Maybe this is kind of the sister thread to "Shumps have grown stale". I agree with that too. I mean, I just think back to way back when, and the quality and amount of great shooters was really something. Now we wait years for anything to some out, and even longer for something to really blow us away. It's depressing.
Well anyway, when was your golden age?