NDX and Sony made me do it!

Yesterday, after walking into my local game store I decided to buy a PSP game. Looking at the collection of games there was nothing that really peeked my interest, glancing over to the left I saw the DS games. I looking at the game, there were quite a few I might pick up IF I had a DS. So I asked the guy there, how much for a used DSi and that was went things went back. I actually started to think about buying it, I spend the next hour and a half thinking if I should buy it and if so what game will I buy first. The first choice was the new Pokemon game black/white. In the end I walked out of the store about 4 hours later, with a DSi and Pokemon Black in hand (I spend the two odds hours playing Pokemon lol)
Now I cannot really stop playing with the features the DS has and when I booted up the store I could not stop laughing the whole time while listening to the music. But the question now becomes, which game is next? Professor layton? Can I jump into the newer game without playing the older ones? One of the many Mario games?