[Tutorial] Playing Nintendo DS in Android
Not to mentioned that some consoles become outdated by a newer consoles rendering your old game collection to be unplayable (I still keep a Playstation 1 emulator so just I could play again my old Metal Gear series). There is a lot of NDS emulator for Androids, but I find that NDS4Droid is the most stable (well, for now) apps. There are other emulators including NDS4Droid that is continuously updated, upgraded, and re-tweak just to ensure the maximum gaming experience when you had the old hand-held console.
Of course, one thing you need to know is that even in PC, NDS emulator is known to have a quite of machine requirement, which is 2 Ghz processing power. So yup, in your smartphone some games might be unplayable due to the limitation of the smartphone processor capacity.