I see a lot of posts about how there were more deserving reps. However, Kid Icarus: Uprising was one of the biggest 3DS games. That means that kids, say, aged 8-14, have grown up with him and likely are happy to see him. Meanwhile, Dark Samus or Link wouldn't do too much for them. Dark Pit is probably one of the best characterized Nintendo character of late, so he's a bit of a treat for the more recent gamer. The way I see it:
Older Gamers Get: Mega Man, Little Mac, Pac-Man, Duck Hunt,
Newer Gamers Get: Palutena, Robin, Lucina, Greninja, Dark Pit, Shulk
Guys in the Middle Get: Rosalina and Luma, Bowser Jr., Dr. Mario?
The games reps are mostly geared towards Nintendo fans before 2010, but Nintendo has had many success stories in the past four years, so why shouldn't they be repped? Yeah, I get that Metroid and DK may be underepped, but cutting Lucina and Dark Pit for Dark Samus and Dixie Kong (as a clone) wouldn't do much for the younger fans and would unevenly stack the characters in favor of the older fans.