I've already got Futari and Espgaluda 2 on the way, an d will most probably try to track down the rest. As I'll probably only get one a month (i'm guessing they're still quite pricy) I'd be interested to know which ones I should go after first.
Highly subjective of course, but here's my ranking:
Mushihimesama Futari Ver. 1.5
Death Smiles
Raiden Fighters Aces
Espgaluda II Black Label
Raiden IV
Shikigami No Shiro III
Mamoru-kun wa Norowarete Shimatta
Shooting Love 200X
Otomedius Gorgeous
Dodonpachi Daioujou Black Label X
Great game, but don't really consider it a shooter, although it is often grouped with them:
1) Dodonpachi Daioujou Black Label X (yes its buggy but still an amazing game)
2) Raiden IV
3) Raiden Fighters Aces
4) Espgaluda II Black Label
5) Mushihimesama Futari Ver. 1.5
Ketsui - Kizuna Jigoku Tachi X will probably be near the top when released.
Anything else I have missed such as Death Smiles I don't really care for to be honest.
The last 3 are more or less even to me. I enjoy them all though. Haven't played any of the other 360 shooters yet. I expect Senko DUO to become my new #1, Deathsmiles 2 will probably tie with the first one, and I have a feeling Ketsui will be above Mushi Futari.
ESPGaluda II
Deathsmiles- Platinum Edition
Mushihimesama Futari 1.5
Do DonPachi DOJBL(if you look past the bugs)
Shikigami No Shiro III
Raiden Fighters Aces
Raiden IV
1.Dodonpachi Daioujou Black Label X
2.Raiden Fighters Aces
3.Raiden IV
4.Espgaluda 2
5.Mushihimesama Futari Ver. 1.5
6.Shikigami No Shiro III
7.Death Smiles
8.Senko no Ronde
9.Mamoru-kun wa Norowarete Shimatta
10.Otomedius Gorgeous