Gameplay - 8.5/10 - Simple and yet complex at the same time
Controls - 9/10 - Very simple, and works with the GC controller
Difficulty - Average difficultly to simply complete, but mastering the game is near impossible
Story - 3/10
Graphics - 8/10 - Dreamcast graphics and somewhat bland
Sound/Music - 8/10 - Music goes well with the game
Replayability 9/10 - Trying to master this game gives it infinite replay value
Ikaruga is one of the best games on the GameCube (or Dreamcast if you can get the Japanese version). It's a standard railshooter, so the basic concept is you move foward in a straight line and kill everything while dodging fire and obstacles.
What complicates this is that there are two types of fire: black and white, and your ship can switch between white or black shields. If your shields match the fire, you absorb it, if it doesn't, you explode. Getting though the game is fairly challenging, and there are three levels of difficultly. The gameplay is not particularly complex. Aside from your shield switching, you only have two guns: a main gun with infinite ammo, and a speical homming laser which charges by absorbing bullets/lasers. Both guns switch polarities with your shields.
The graphics are not that impressive, but it's necessary due to the polarities. The backgrounds are generally a rather bland shade of brown, and almost all enemies are black & red or blue & white. This necessary to be able to see what polarities everything is. All of the bosses are graphically impressive though.
This game is lacking in story, but as a shooter, it doesn't really need one to be a great game. In the original Dreamcast version, there were cut-scenes between levels explaining the story, but they were cut out for the GC version.
The true challenge is the game is not simply beating it; it is in getting a high score by chaining your kills (chaining is killing three enemies of the same color in a row) This adds a lot of strategy to the game. And, if that's not enough of a challenge, it is possible to beat the entire game without firing a single shot, though very few people can do it (I'm not one of them, unfortunatly)