Very good for what it is, a large collection of old-school 8 bit games.
Anyways, you are given 4 challenges for each little game which resembles other popular games. I thought of it like how at the store you can buy the real brand cereal, or the gigantic bag of cereal by some copy-cat cereal for less. Although these games aren't necessarily worse than their original, it's hard to just ignore the fact that they aren't the original versions of the game. Then again, if your just looking forward to this game to have a ton of different games on your DS you'll probably get over it quickly.
I only got the chance to play the game for 2 hours or so today but I've enjoyed it. It's given me a well needed break from constant amounts of Final Fantasy Tactics A2. I unlocked all the challenges for the first game, and started working on the 2nd game. Both of them work fine and I only experienced a hiccup on the Galaga-clone game when I had a screen full of enemies.
One thing I have to say which kind of disappointed me was the complete abandonment of the touch screen. I realize it's hard to implement the touch screen on games that were designed for arcades over 20 years old but completely ignoring the screen just feels awkward. Again though, I'm being nitpicky and these are relatively minor gripes.
Retro Game Challenge does a good job for what it is. Having a bundle of games in a collection with a bigger story behind it is a refreshing idea instead of just giving a list of classic games you can instantly play out of the box. I would recommend this game if you like old school games and like playing games on the go.
But if your someone who's debating whether to get this game or the Sonic UGC (which probably narrows it down to about 5 people in the world haha), get the Sonic game.