Metroid, but now with online multiplayer.
Story:
Not really a story available, unless you count the single-player mode. Basically you have to hunt for the "ultimate power" while 6 other hunters stalk you to steal whatever they can from you. You'll run into them at periodic times, so watch your back.
Gameplay:
Multiplayer is the big factor here. You can play capture the flag, bounty hunter mode, the prime hunter, or just a regular old deathmatch. Really fun especially if you have friends with you.
The new addition of 6 other hunters, with unique backgrounds, designs, status screen interfaces, weapons and tactics is what really makes this game fun. Play as a cloaked sniper, a flame-grenade launching behemoth or simply go all out as Samus herself.
Control:
The DS screen allows easy aiming and shooting, while the directional pad allows smooth control. However, your shoulder buttons might die pretty fast...
Rent or Buy?
Buy if you enjoy multiplayer gaming or Metroid games in general.
Avoid this if you are looking for a good single-player story campaign.