I will ignore undubs and translations here (
http://www.romhacking.net/?page=tra...=20&order=&dir=&title=&author=&transsearch=Go ) as most of those for English are fairly well known.
Zelda and starfox dpad lessening hacks. For the former go with the Greiga Master stuff rather than the earlier stuff. Haven't tried the Trauma Center Under the Knife 2 Wii Controls Hack but I will note it in passing as I thought that would do well.
Castlevania touchscreen lessening hacks (makes seals trivial, sorts ice and other good stuff for the first, others also have things here).
By similar token Custom Robo Arena Redux might be worth exploring, especially if you rinsed the original.
Tetris DS vs cpu mode music tweaks -- the mario theme is iconic and all but if I have a choice between that and various Russian folk songs (or Zelda or whatever else you want)...
Dragon Quest 5 monster trainer.
http://jeffludwig.com/dq5ds/download.php . Tweaks things to actually be more about training.
Final Fantasy Tactics saw a nice mod
https://gbatemp.net/download/ffta2_redesigned_-updated-2015-01-09.33301/
Cheats and save editors in general can solve a lot of issues.
If you like Fire Emblem, Mario Kart hacks and New Super Mario Brothers enough to want to play more then there are some interesting things there, both in terms of alt games and tweaks (
https://gbatemp.net/download/fire-emblem-shadow-dragon-sync-patch.27502/ ). I would not be particularly concerned if I never played any of those again though at this point. Haven't followed what goes for Advance Wars on the DS as far as hacking though. Haven't seen anything particularly interesting in the pokemon world like I saw before on some of the older games and most of them were sprite tweaks, or all pokemon in one version type hacks. If Dragon Ball Z is your thing then there are some editors there which might allow you to mix it up a bit, though I might be remembering the GBA ones. Some other games also have tools (Dragon Quest 4 if memory serves) that do good things.