gamingdevil on 14 November 2007
It depends on what games you like, my lists:
Wii:
RE:UC
Super Mario Galaxy
Medal Of Honor Heroes 2
Metroid Prime 3
Zack & Wiki
Fire Emblem Radiant Dawn
DS:
Dementium
Zelda: Phantom Hourglass
Dragon Quest Monsters Joker
Ultimate Mortal Kombat
Megaman ZX Advent
Rayman Raving Rabbids 2
These are the games i play at the moment and according to my taste they all are must-have titles.
Note to Wii owners: Do not, i repeat, DO NOT under any circumstances buy Rayman Raving Rabbids 2 for the Wii with the impression it's like the first, the game is an awful bore-fest. 
