The stickied topic is still rather relevant. To be honest there hasn't been much development recently with regards to emulators. You still want to be looking at NES DS, SNEmulDS, jEnesisDS, and Lameboy for the main systems that people emulate.
you forgot neods. an amazingly surprisingly great neo geo system. plays games at full speed. theres only one game i cant get to work 100%(its at full speed) and thats metal slug 5, the volume for the background sound and the song is backwards. meaning that the background sounds are way louder then the music. every other games work perfectly.
Personally I can't live without SCUMMVM, it works really well on the DS with stylus controls.
I don't like jenesisds, because it runs in native genesis resolution, and doesn't shrink it to DS resolution size. Which means certain percentage of the screen is cut off horizontally. Also it doesn't support 6button pads (or rather, it supports them very poorly), so you cannot play Lost Vikings and such.
SnemulDS can crash your micro SD. I'd stay well away.