Great update to an ancient game. No brainer if you're a fan of the first, try it first if otherwise.
Graphics are serviceable but when compared to today's standards they are fairly austere. Compared with the original (which is actually included with the game!) however it is a very nice modernization.
Gameplay has been updated and really shines with the dual analog sticks of the XBox 360 controller. In it's first incarnation your ship was controlled by the mouse and firing was handled based on the direction and velocity your ship was moving. It was a fairly strange setup that took quite a while to master. The new setup makes everything pick up and play and really makes the whole experience smoother.
The DLC for the game is a bit weak with two sound effect packages that simply aren't very good. (Of the two, the animal sound effects is the better choice). However the game skins really have a big effect on the game. I personally enjoy the Sketch skin.
The best bit of DLC is the generically named Crystal Quest Xtreme plugin which really cranks up the difficulty and the points.
The bottom line is that if you are a fan of the original this is a fantastic update to an old classic. If not though, Crystal Quest doesn't do much to stand out from the proliferation of Robotron clones that predominate on XBLA.