I got bored and wrote this, although it is not quite finished (final version should have setup guides and some screens) it may help here:
GBA/DS nes emulation guide:
There are several emulators available for the GBA and for the DS that enable you to play NES/Famicom games (The famicom disk system, aka FDS, is not always supported but it is done in some emulators).
GBA Section:
There are multiple emulators here and as many are open source there are a few side projects too, the biggest issue for the GBA emu line is the screen resolution of the GBA is not the same as the NES so things get scaled.
Pocketnes (Original):
http://hem.passagen.se/flubba/gbadown.html
This is probably the most well known and highly regarded NES emu for the GBA and with good reason. No FDS support, the lack of a few (relatively unused) mappers and the unusual scaling mode (affects text in some RPGS but is better overall) are probably the biggest detractors.
Pocketnes (Dwedit): (GBAMP SD/CF and multiboot cable versions available too)
http://dwedit.home.comcast.net/
Seen as Pocketnes is open source others have taken the source and added to it.
Pocketnes is fantastic and this is the icing on the cake (cheats and a few more mappers and tricks).
Pocketnes (Kuwanger):
http://kuwanger.net/gba/pocketnes/
Currently based on a slightly older version of Dwedit's pocketnes this version has compression and is also very nice.
Infones Advanced
http://www.geocities.co.jp/SiliconValley/5604/infones.html
Not bad but pocketnes is better.
Unnoficial Famicom Advanced
(I have no homepage but http://gbaemu.dcemu.co.uk/unnfamicom.shtml has it)
What HVCA was called before it changed to HVCA, use HVCA instead.
HVCA
http://mc68882.s53.xrea.com/
You will probably want a guide to this so:
http://wiki.pocketheaven.com/Hvca
In the land of GBA code nes emulators pocketnes is king, lets just say this is a major threat to that position.
It is in Japanese so that is why I linked the wiki article.
FDS support (with diskrom.sys file) and in some respects a nicer scaling mode as well as more mappers than pocketnes makes for a damn fine emulator.
Famicom Advanced
No homepage
http://gbaemu.dcemu.co.uk/famicom.shtml
Early stage, not really worth considering
DS Section
These a not quite as advanced as some of the GBA stuff but the added power makes for some truely impressive emulation. Naturally you will need some form of (no)pass(me) device to run this, if any emulator makes use of special libraries/certain flash carts I will say so.
NesDS
Nowdays inactive but has a nice scaling mode, only real detractor is lack of save making support (you can load saves if they are in the SRAM)
http://www.cs.utah.edu/~tew/nesDS/
NesDS (modified)
No homepage as it was released in a forum thread:
http://forums.maxconsole.net/showthread.php?t=25181
Download:
http://www.playeradvance.org/forum/showthread.php?t=3729
Added save support for a few flashcarts, I would advise reading the threads linked for more info. If you can get it working probably the best DS nes emu and if games are all you want probably the best way to play NES games on your GBA/DS.
Retrobox
http://www.geocities.com/retropoint/
No public relase as of this point in time. A fair potential though.
NesterDS
http://www.telefragged.com/thefatal/index....t=inc_si_ds.htm
One of the first nes emulators and a DS port of the nes emu known as nester, not really worth the effort.
Midori
Download here:
http://www.maxconsole.net/?mode=downloads&categoryid=114
Released as an entry in the neoflash coding contest, no sound but otherwise being halfway acceptable means this goes into third place quality wise. I would probably consider a GBA code emu though.