You say it like that and it sounds absurd not to buy it, but at the same time if it turns out that I only like GnG then it's a very expensive game!
I just picked it up and haven't played about half the games before. Impressions:
Vulgus: Typical archaic shmup. Good if you like that, I guess, but I can't really go back to them considering how far the genre has come.
SonSon: Cute little prototype to more advanced run and gun shooters like Metal Slug. Pretty fun and good music.
Higemaru: Sort of like a more puzzle-y Bomberman. I like this.
1942: Archaic shmup again. See Vulgus.
Savage Bees: Vulgus again. Annoying music.
Commando: Plays like GunSmoke except you have to aim your guy where you want him to shoot, which makes it a little more annoying to play. Still decent.
Ghosts n Goblins: Everyone knows this one.
GunSmoke: Same here.
Section Z: I guess NES fans know this one. I think it's pretty cool.
Trojan: I've always hated this one with a passion.
The Speed Rumbler: Driving and shooting game. Annoying and hard. That chiptune crescendo made my ears bleed. Do not want.
Legendary Wings: It's Xevious with an ancient greek theme, or something. See Vulgus.
Side Arms: An ancient shmup that actually moves fast and feels hectic! Plus, I found a hidden item that made my mech more badass right off the bat in the first level. I liked this one immediately.
Avengers: LOL. Goofy, stupid fun, but a relentless quarter muncher. The very first enemy grabbed me and instantly killed me. I figured out later that I can buttonmash my way out of grabs but by that point they'll have gobbled up half my life bar.
1943: More ancient shmup boredom.
Black Tiger: Probably the coolest game in the collection, at least considering most people haven't played it. It's a precursor to Magic Sword, a sort of RPG-y sidescrolling platformer.
All in all? I guess not worth it unless you just love ancient history shmups. At 1200, though, I'll get my money's worth from GunSmoke, GnG, Black Tiger, Section Z, Higemaru, SonSon and Side Arms, and I'll probably have more lols playing Avengers. I would understand if someone doesn't like Higemaru, SonSon and Avengers though. Emulation is pretty much perfect and there's a wealth of options for each game.