For DS:
The World Ends With You:
Excellent story, innovative battle system, colorful artstyle and music choices. Extremely customizable, even with the difficulty: lets beginners storm through it, and rewards those who choose to challenge themselves.
Yes, the beginning shows the protagonist as moody and antisocial. Not only is it done right though, it changes relatively soon as well. Just don't spoil anything for yourself while playing it.
Shin megami Tensei: Devil Survivor
Great story, multiple plot paths. Artstyle is nice, if not innovative. Music is good, some of it's rather catchy. Great characterization of all characters, as well as letting you characterize the main character however you want (and it does have an impact on story).
Battle system: classic grid style, but teams instead of single units per square. Winning a battle depnds very much on strategy and abusing weaknesses as opposed to grinding to increase levels. In fact, there seems to be an anti-grinding system in place, where experience needed to level up raises exponentially instead of linearly.
Mario and Luigi: Bowser's Inside Story:
Cute, funny, fun battle system. Music is amazing. Bowser is amazing. F... main villain is amazing. You really can't go wrong with this.
Pokemon HeartGold / SoulSilver:
Fun, possibly extremely nostalgic. Lots of polish everywhere, you won't get bored.
Don't know bout the Xbox. There are no good RPG's for the wii.