Why haven't you played this?
BGE deals with a woman named Jade, who runs a orphanage with a pig-human named Peyj. The planet is being bombarded with creatures called DOMZ, who take the souls of their victims. The game begins as Jade is defending the children from a DOMZ bombardment, and teaches the basics of combat. The Alpha Sections/ Hillys's Army if you will secure the area and help Jade and Peyj to the surface. Jade soon gets a disk mail telling her to meet a man on an island, where she soon finds there is more to the world than meets the eye.
Two things Ubisoft is well known for over the past few years are the amazing combat of Prince of Persia, and the stealth of Splinter Cell. BGE makes great use of Prince's combat style, as Jade can attack using the a button but using the analog stick can attack anywhere in a 360 degree direction. Stealth plays a role in the second half of the game, and plays well. Also there is a "Pokemon Snap" sorta portion of the game, as Jade gains money by catalogueing creatures for the local science community. Pearls are also collected and used at the Mammago Garage to furnish your hovercraft.
Most of the game is spent with a partner character, who will help you along the way. Jade can give or take away items such as food, and health boosters that work somewhat like Heart Containers in Zelda games. There is a lot of teamwork involved, but the characters do not get in the way, and sometimes hold their own.
The graphics on this game are pretty amazing. The characters all seem to have different facial expressions, and react differently depending on the situation and what happens around them. The first time you see a huge whale jump out of the water, I dare you not to go "Woah". The music is memorable and many of the songs you will be remembering long after this game is over.
The game is over somewhat early, but due to a great story, amazing gameplay, and fantastic presentations, this game will be one you will be more than ready to pop in again a few weeks later.