If the 3DS wasn't two full generations behind (basically) where modern devs are at, I think a lot more devs would like to make games for it.
It's just too far behind to give the popular modern franchises to give the same/similar type of game play experience the bigger franchises are known for today so publishers don't bother with it in the West.
If Nintendo can make a handheld that's 1.5x the XBox 360/Wii U even .... I think a lot of Japanese devs would be willing to port to the handheld (and then have a higher spec version for the console that's roughly at full parity). And you'd have I think quite a few Western devs too.
Sure not all of them, but getting COD, Madden NFL, FIFA, some Star Wars games, maybe an Assassin's Creed spin-off, Rayman ... would be a much better than what Nintendo is getting today on either the 3DS or Wii U.
They have to take advantage of the huge advances in mobile chip tech though. They are making iPhone/Android games and still can carry the N3DS for a few more years to serve the lower end market, I think they need to go upmarket with their handheld.
For people who say the 3DS didn't sell well at a slightly higher price, I say neither did the original DS. People forget now but the original DS was selling very poorly post-launch too, in fact the $250 PSP was outselling it in a lot of months, Nintendo had to drop the price of the DS to $129.99 too.
If you got Zelda and Mario in your launch window you should be able to ride that for the first 6 months and then production costs will scale down, especially if you're using the same family of CPU/GPU/RAM for both systems (the advantages of buying in bulk).