Am I missing anything?

[jpolz]

Since I installed HDLoader onto my PS2 and enabled me to play import games, I've purchased what I consider to be the "heavy hitters" for the platform:

ESPGaluda
Ibara
DoDonPachi DOJ
Mushihimesama
Psyvariar - Ultimate Final

I also have every domestic release as well.

Are there any other titles worth getting? I don't care if they are available on other platforms, so long as they are of equal quality or offer something not found in the original.

[Ceph]

Homura and possibly Raiden III (some like it). Then there's Shienryu, Dragon Blaze and Strikers 1945 I+II (in case you don't have it already for PS1).

[BulletMagnet]

There have been a couple of "What PS2 Shmups Should I Get?" topics recently, if you look around there should be some info in there you might use.

[captain ahar]

i'd really suggest trying Shienryu. fun game, raiden-like gameplay, and an absolute bargain at around $20.