PSP has Disgaea too.
SNES emulation is mediocre at best for the NDS. Again, if emulation is important to you, PSP is the way to go.
Also flashcards have dropped in price significantly. If you're paying any more than $20 for anything not made by CycloDS, you're getting ripped off.
And yes, Colors! is excellent. DSOrganize is a no-brainer as well - calendar, notepad, doodlepad, file browser, web browser, irc client, media player (even plays MODs and stuff), etc. Pretty much makes your DS a gimpy PocketPC. Nitrotracker is cool too; you can make samples with the built-in mic! That and/or Korg DS-10 might be something you'd find useful if you get musical ideas on the go often.