eXceed 2nd - Vampire REX, the sequel to Gun Bullet Children, has everything that the 1st one lacked: Astonishing graphics, a soundtrack you'll want to own, and tight gameplay.
The game is story-wise a sequel to Gun Bullet Children, but this time you'll side with the vampires against the Church and their Gun Bullet Children. You play as Ria File, a half-human, half-vampire (aka a deviant bloodline). She has the ability to shift polarity: switch elements to absorb bullets of the same element while the other type becomes fatal. This is a mechanic that shouldn't be unknown to Ikaruga players. The game also has a dynamic difficulty implemented, whereas long survival and scoring gets you in a higher difficulty while playing, and dying reduces the difficulty. The overal difficulty of the game is okay. It might be tricky at first for newer people, but you'll get the hang of it quickly.
Although there isn't much to the story in most danmaku shooters, this one had a story i liked. The game references characters from the previous game as well. Just like the previous game, the characters have voicing in Japanese, and unlike Gun Bullet Children, this one has an official translation in the game.
The soundtrack was made by Saitama Saishu Heiki and Shibayan, well known names in the doujin world, and this soundtrack delivers, just like their other works. The boss music fits rather well with the bosses' personalities or significance in the story, whereas the stage music either takes it a bit easier or just gets really tense to prepare you for your next big challenge.
This game is just fantastic and is among my favourite danmaku shooters now. They really outdid Gun Bullet children by far. You can get it for 6 EUR, but i'd be willing to pay double price for this game.
Also, i didn't find the OST on Steam, but you can purchase it from the tennen-sozai site