I think that is a poor generalization. Compared to the sales of PS/XBox, most 3rd party games sell unmistakenly better on those than on Nintendo, but that doesn't mean 3rd parties can't prosper there. Even leaving the clear successes on Nintendo handhelds (Monster Hunter, Youkai Watch, Bravely Default, Professor Layton, Ace Attorney, Sonic games...), 3rd party console games can reach a decent number of sales on Nintendo consoles. Rayman Legends on WiiU is the second best platform for the title, the NFC games are the strongest on Nintendo, Just Dance is still kicking after all this years...
You might say that most of those aren't titles that pick the interest of the average gamer, but I don't think that's a problem. Different consoles have different auiences. RPGs sell better on PS devices than on XBox devices, and Shooters sell better on XBox devices than PS devices. And both platforms get both genres anyway.
Nintendo platforms might not be the best selling platform for 3rd party games, the problem is they didn't even try. Particulary with the WiiU. The GCube had some great, albeit small, 3rd party support, and the Wii just kept getting game after game, suited for the bulk of its userbase. The WiiU got for the most part either older games that people owned already or late ports of games with less support than the other versions, so people that were interested in those just got them elsewhere. And after those ports failed, publishers abandoned the system. If 3rd parties pushed more games suited for Nintendo's audience in a way they keep the quality and support, the games would sell. Maybe not as much as the PS/XBox versions, but they could make a profit.
sure it will get the same 3rd party games the wiiu/3ds got. Skylanders, monster hunter, just dance and co.
I was more talking about aaa third party support (gta, fifa, cod, witcher, elder scrolls, fallout, assassins creed, mirrors edge, mass effect, deus ex, battlefield, battlefront, dragon age, diablo, Destiny, Far Cry, Watchdogs, Batman, The Division, Madden, Nba, Mortal Kombat, need for speed, just cause, bioshock)