I do most of my gaming on a Retroid, which can run a lot of PS2 games well, as well as obviously earlier games. I really liked the GBA Macross game - you got to level up ship stats after each stage to make it more durable, or your weapons stronger, and shit like that.
What other shmups have similar mechanics? Dont care if theyre horizontal or vertical. I already have Radiant Silvergun's Saturn port loaded on my device, so inb4 that one.
Ayyy came in here to mention UN Squadron. Another Capcom shmup Forgotten Words has shops were you can buy blasters and options and such.