depends sometimes they can be dumped in a couple of days, weeks perhaps months, it just depends on who feels like dumping it, its not usually a long wait
if your lucky you get pre-release dumps
you can dump the roms from a ds with hacked firmware, some flash carts with the right software and a adapter for the pc
like this
[quote]or is it the emulators that have to suit the games?[/quote]
no DS emulator is perfect, most are developed by reverse engineering in some way, that inherently causes the emulator to not always work 100% also none are complete so its neither expected that they will work 100% either.
hope i answered your questions