At this moment, there are lots of NDS games in the market. Especially, pokemon series.
As you can see all above, those are fourth generation of Pokemon and there is coming next generation of Pokemon which consists of Pokemon Black and White. They are also compatible with NDS (exclusive.) Not just that, there are other games such as Kingdom Heart 358/2, Yu Gi Oh! 5Ds. WOW!!, it’s so great, isn’t it?
So, then after you have emulators, another thing you need is Rom. There are many websites around the world. Use Google for it (ha ha).
One thing, rom is pirated. So, almost rom have problems (hang, cannot boot, game is not complete, etc.) You have to read description carefully what you must do before playing. You might need patch, update firmware of emulator, and much more. Then please not complain because you are piracy.
Suggested websites:
1. Soi13.com
2. Happy2You.net
PS. please SUPPORT genuine hardware and software.