It can be remembered that during the 3DS's first year, they quickly reduced the price from $249.99 to $169.99. Nintendo did not leave early adopters hanging, they gave them 20 free games which consists of classic NES and GBA games. If you see where I'm coming from, Nintendo did a lot for the fans.
Sony on the other hand refuses to drop the price for the Vita. They keep saying that they're satisfied with the Vita's sales. Maybe they really are, but for how long?
Recently, we see a lot of advertisements for the 3DS with celebrities like Penélope Cruz and Robin Williams in it. Nintendo also does a regular Nintendo Direct conference to update fans on upcoming releases for both the 3DS and Wii U platforms. Now, I can't remember a single advertisement done by Sony. Surely, they must have done something during the past six months or so. Bottom line, Nintendo is doing a great job marketing.
So, with the fan base that Nintendo managed to build for themselves, they can now be friendly with developers and publishers. They can give the assurance that their games will sell, and it doesn't have to be in HD or try to compete with tablet devices when it comes to touch capabilities. The games only have to play nice — good, quality gameplay.
Lastly, Nintendo was able to capitalize on most of their existing IP's. So even when there was a drought of developer support from the start, the 3DS was able to stand on its own with first-party games like Mario and Zelda.
How about you? Do you think that the 3DS is succeeding and the Vita is not? Why and what do you think Sony have to do to help the Vita succeed?