The PS3 started with the biggest loss of market share in history, but managed to tie the 360 in world sales at the end. Not to forget the really bad design choices and pretty lacking PSN at the beginning.
The 3DS had a very slow launch that forced a $80 price drop only months after release. Many complained about the lack of games and wondered whether Nintendo still had game (pun intended). Now it's the top selling console of 2013.