It's time to set things straight.
The reason I say the storyline doesn't go very far is because of the repetitiveness of the gameplay.
The gameplay is pretty straightforward. As you play through the game you can retrieve pieces of your destroyed Legion called Thanatos (destroyed by Victor at the start of the game).
You mostly play as Seig, but can later on in the game play an intermissional stage as Arcia.
This is a typical stage run-through: Enemies respawn, you must annihilate all enemies and targets, grab items and Thanatos chips, and fight a boss. During each stage, gates will be locked and only when you complete the assigned task do the gates unlock for your character to proceed forward.
For the first few stages, this was actually kind of fun, but that is how every stage pretty much operates, with a cutscene here and there. It got repetitive very fast.
Though, gameplay is pretty smooth and I found no problems in playing.
The music, like in Devil May Cry, is very well done, but the battle arenas are boring and dull. There wasn't a whole lot of creativity in the graphic layout.
Graphic-wise, I only really enjoyed the 'dark' cutscenes and some of the attack moves.
All in all, I gave Chaos Legion the rating I did because of repetition, good music and graphics, and so-so storyline.
Although Gamespot gave Chaos Legion the mediocre rating, I don't believe it was a terrible game. It was still a fun pastime and the gameplay, music, graphics, and storyline still are worth looking into.