Not many of them are around? *Ahem*
On PS3 alone:
Blast Factor
Super Stardust HD
Rocketmen [Get the other four before that one, I heard it's quite bad]
Novastrike [Not sure about this one]
Everyday Shooter
On X-Box 360:
Geometry Wars [Obviously. That's also the only one I know]
PSP:
Polygun Wars (Homebrew) [Geometry Wars for PSP]
No Gravity The Plague of Mind (To be released) [Demo available for CFW]
R-Type Command (PSN Game)
Many other homebrews

I wouldn't say it's dead just yet.