Okay, first off, I know what you're thinking, and I agree, 3DS has enough remakes and ports on the way as it is, and of course 3DS is fully backwards compatible anyway. But hear me out on this, just a thought of mine.
It would be fair to assume that the DS has an immense library of games to its name, and it wold probably take a lifetime to play through them all. It would also be fair to assume that many of them are out of print, or have high costs from importing or general rarity. And the 3DS no doubt offers lots of new features over the original Phat and Lite models that could easily benefit older games should they be updated for it (eg. Cleaner visuals like FF3 on iOS, stronger wifi features, 3D update, Analog stick).
So, my line of thought is, what if Nintendo, much like Sony and Microsoft are doing with their more recent backlog, offer downloadable enhanced DS games through the e-Store at a lesser price? That way, the shelves won't get clogged up with older games, allowing new titles to get some limelight. And I'd wager a lot of people would relish the oportunity to take around multiple DS software in non-cartridge form.
Some games I think would benefit;
Super Mario 64 DS- Two words: Analog Stick. The DS launch title would undoubtedly have been superior to its original if not for the controls, one bit of coding can fix that (again, I know the stick can be used with the game already, but it isn't true 360 degree movement). Seeing those painted worlds in 3D would certainly speak for itself, and just imagine the potential of those Minigames with online and leaderboard support.
Okamiden- Yep, a recent release, but the timing of it sandwiched between Pokemon Black/White and the 3DS makes me believe that it'll become an expensive rarity in a few months. Don't know enough about the game to say how the 3DS could boost it, though I'm sure those who have played it can offer some suggestions.
Ace Attorney games- Now these buggers already are fairly rare and go for quite a bit, despite being years old. Capcom have already shown that Phoenix is up for downloadable views with the iOS and Wiiware stores, so it wouldn't be a huge stretch to imagine they'd stick it on the e-Store if they wanted to. Plus, Objection! finger in 3D? Sign me the hell up.
Thoughts?