Not to be a downcast beat, but Animal Crossing has pretty much stayed the same (graphic wise) since it's first incarnation. They may improve on some of the elements, like weather, but the same goofy models (albeit, updated and better animated) appear in all incarnations of the series. I don't think it'll be different for the 3DS.
If anything, expect a lot of the first titles from all developers to be a bit iffy. They'll all test out the 3D to see how it fares - and for some games, I'm sure it'll look great - in particular, I'm looking forward to a Metroid Prime Hunters style game where missed bullets and such whizz by in 3D. I can imagine playing some kind of game in the desert or something, and whenever you walk, sand is kicked up and displayed - something like that can be annoying over time, I'm sure, but in moderation, it would be pretty cool. But, at the same time, I can already see some developers "coughEAcough" going a bit overboard with the 3D effects outside of the box. I'm just glad you'll be able to turn off the 3D after a while.
Also, Starfox plz. Really. Either announce one for the 3DS or one for the Wii, but Jesus Christ we need one. Not that Command was awful - it just wasn't what anyone wanted. I'd prefer an Assault style aircraft method, meshed together with a "Gears of War" styled land section. (Mainly it's cover mechanic and reloading - please, no chain saws.)
I'd very much like a new 3D Mario game, too. Mario Galaxy Portable? With 3D effects? If anything flinging star bits and watching that gold coin dust fly up upon collection would look sweet.