Pokemon Diamond or Pearl.
I did not like Pokemon. My husband bought my ds last year too and he bought me Brain Age (which I also like) and Pokemon Pearl (because he didn't know what else to get). I have recently started playing it and OMGosh it is addicting. I LOVE this game - especially now that I've figured out there is an actual story line and point to it. At first I thought it was just running around catching Pokemon, but no, you have to battle these Galactic Grunt people because they are trying to destroy the place to make a new world.
My kids have Pokemon Diamond. The only difference between Diamond and Pearl is the #1 pokemon thingy is a pink and white godzilla looking thingy on Pearl and is a blue horse/lizard thingy on Diamond. Mike bought me Pearl because I like pink.