Sigh
This might sound harsh, but I'm not looking to insult, but rather offer constructive critism.
Sadly there was no real improvement over the first game. While I am a fan of games of this nature, nothing special is brought to the table. Gradius' nintendo days offered more. I understand this is a flash, but add some variety.
There are currently two weapon types in the game. You have Fire/Lasers/Rockets and they do the same exact thing, just in a different color. Then you have Shurikens which are the only weapon worth using.
The first boss required upgraded weapons for its 2nd phase so you could hit the rockets to actually damage him. The second boss was just a generic "cover the screen in bullets and pray you can dodge".
This game has potential, but the lack of flavor is whats killing it. Add variety, make the weapons actually have a significant difference beside their charged form. Make it so it isn't a game of fill the screen with 700 bullets at once. You'd have a winner if the game had variety.
This isn't the first shooter flash to hit newgrounds. There are others that have the basic concepts and then expand upon them to make great games. You have the basics covered, now expand and you'd easily be able to have a top game on this site.