I Want
Call of Duty 4: Modern Warfare DS (DS)
The DS incarnation looks awfully nice, but ultimately doesn't hold up well between lame enemies and jerky movement. Hit up its console siblings instead.
I'm playing
Kirby Super Star Ultra (DS)
Kirby faces a number of adventures where he must run, float, copy enemies and use Helpers to fight the likes of King Dedede and Meta Knight. It may become same-y ...
Forza Motorsport 2 (Xbox 360)
Loaded with customization and options, the best and most authentic racing experience in recent memory burns donuts around any other driving game on the Xbox 360.
Brain Age 2 (DS)
The doctor is back with more fun tests and exercises to enhance your noodle.
Mario Super Sluggers (Wii)
Super Sluggers is as solid a game as you'd expect from any sports title with Mario's name attached.
SimCity Creator (DS)

A fun diversion, but turn to the PC release if you want something much deeper.

I've Beaten
Mario vs. Donkey Kong 2: March of the Minis (DS)
Boss around a group of wind-up, mini-Marios so they don't accidentally kill themselves. Kind of a hands-off puzzler, but could still offer up some decent headaches.
MySims (DS)
The Sims meets Nintendo's DS in a cute-ified version of the world's most popular series.
Spore (DS)
Maxis decided to drop some scraps of its massive game monster Spore onto the DS with middling results.
Guitar Hero II (Xbox 360)
The sequel to Guitar Hero promises 55 new songs and the option to jam with friends on bass, rhythm or lead guitar tracks.
Guitar Hero On Tour: Decades (DS)

The second round of Guitar Hero on the DS is much like the first: same wacky, cramp-inducing controller attachment, same spotty strum detection, but same fundamental rockingness.

Halo 3 (Xbox 360)
Master Chief returns to fuel another round of alien-smashing blood-bathery. What are you waiting for? Finish the fight!