(Oct 11, 2014)

Pokémon Y: 181:16
Super Smash Bros.: 44:02
Fire Emblem Awakening: 31:26
The Legend of Zelda Ocarina of Time 3D: 27:04
Super Mario 3D Land: 24:03
Mario Kart 7: 22:59

Not much compared to others. That Pokémon though...

If I put that much time into Pokémon X or Y I probably would've killed myself by now.

Anyhow, I think it's Pokémon White 2 at over 150 hours and Animal Crossing is second at 100-something.

fire emblem awakening 237:51
Pokemon Y 81:06
Pokemon white 2 74:30
DK Country Returns 3D 66:51
Super Street Fighter IV 38:21
Links Awakening (virtual console gbc) 36:57
Etrian Odyssey (not finished yet) 31:37
Super Mario 64 DS 30:11
Mega Man 2 14:43
Zelda Link Between Worlds (not finished yet) 14:04
Wario Land 2 11:40
Super Smash Bros 11:01
The Legend of Zelda (nes) 10:37
3D Classics Kid Icarus 9:06
Super Mario Bros 8:29
3D Sonic the hedgehog 7:51
Super Mario Bros 3 7:41
Castlevania (nes) 6:19

I think Nintendo has information of how many hours a game is played in average, and the reason why Fire Emblem has no many characters in Smash even though it is a niche franchise, is that they see the people who buy those games play them for an enormous ammount of time.

My top 5:(only 3ds games)
1.- Pokemon Y at 568:52
2,- Shin Megami Tensei Devil Survivor Overclocked at 187:28
3,- Shin Megami Tensei 4 at 149:58
4,- Kingdom Hearts 3D at 107:31
5,- The Legend of Zelda Ocarina of Time 3D at 67:11