Mines:

1.Kid Icarus: Uprising (314:49)

2.Animal Crossing: New Leaf (218:47)

3.Zelda: Ocarina of Time 3D (111:26)

4.Resident Evil: Revelations (61:29)

5.NSMB2 (57:05) *can't believe it o.o*

6.Luigi's Mansion: Dark Moon (42:59)

7.Super Street Fighter 4 (36:49)

8.Super Mario 3D Land (25:54)

9.Mario Tennis Open (24:27)

10.Donkey Kong Returns 3D (23:41)

11.Mario Kart 7 (21:20)

12.Heroes of Ruin (20:27)

13.Mario vs. DK Minis March Again (18:28)

14.Lego City Chase Begins (16:24)

15.Amazing Spider Man (14:26)

16.Pushmo (9:18)

17.Spider Man: Edge of Time (8:44)

18.HarmoKnight (8.28)

19.Marvel Pinball 3D (8:10)

20.Kingdom Hearts 3D (7:53)

So that's mine, how about you guys?

I don't have my 3DS with me... But the game where I spent more hours was on Monter hunter 3 Ultimate, Etrian Odyssey 4, Resident Evil Revelations, Shin Megami Tensei 4, Zero Escape Vrtue's Last Reward and... I forgot the rest but those are the ones where I spent more hours.

EDIT: Oh and Pokemon X!

I doubt I've spent more than 30 or 40 hours on my 3DS...

That's ok :3

Excluding non-gaming content like the internet explorer and download play.

1. Fire Emblem: Awakening (127:04)
2. Etrian Odyssey IV (70:46)
3. Fire Emblem: Sacred Stones (62:13)
4. Tales of the Abyss (60:58)
5. Mario Kart 7 (52:04)
6. Pokémon X (51:46)
7. Professor Layton and the Miracle Mask (43:12)
8. Bravely Default (42:05)
9. Ocarina of Time 3D (41:21)
10. Pokémon White 2 (39:13)
11. Virtue's Last Reward (38:29)
12. Kingdom Hearts 3D (37:26)
13. Picross DS (36:41)
14. Professor Layton and the Azran Legacies (36:28)
15. Final Fantasy: 4 Heroes of Light (32:38)
16. Animal Crossing: New Leaf (28:57)
17. Zelda: A Link Between Worlds (24:39)
18. Metroid Fusion (23:12)
19. Rhythm Paradise (20:24)
20. New Super Mario Bros. 2 (18:00)

Holy crap. More than a hundred horus of Kid Icarus? Personally I get tired of games too quickly and rarely go over 25 hours.

Here's mine:
1.Fire Emblem Awakening-273:32
2.Fire Emblem: The Scared Stones-258:42
3.Pokemon X-119:30
4.Samurai Warriors:Chronicles-61:23
5.Pokemon HeartGold-56:43
6.Shin Megami Tensei IV-46:12
7.Pokemon Black 2-45:31
8.Devil Summoner:Soul Hackers-45:03
9.Devil Survivor 2-41:12
10.Fire Emblem:Shadow Dragon-40:47
11.Pokemon Diamond-40:45
12.Panzer Tactics DS-39:03
13.Devil Survivor-37:09
14.Resident Evil: The Mercenaries 3D-33:09
15.Ghost Recon: Shadow Wars-33:03
16.New Super Mario Bros 2- 31:49
17.Tales of the Abyss-30:17
18.Star Fox 64 3D-29:08
19.Etrian Odyssey IV-28:22
20.Project X Zone-26:19

I I don't have 20 games to list, but I well list my top 10:

1-Fire Emblem Awakening(249:42)

2-Pokemon X(236:38)

3-Rune Factory 4(156:13)

4-Animal Crossing New Leaf(112:20)

5-e-Shop(76:15)

6-Luigi Mansion(56:57)

7-Zelda Ocarina of Time(45:08)

8-Mario & Luigi Dream Team(40:53)

9-Super Mario 3D Land(35:23)

10-Mario Kart 7(34:36)

wtf? Where is Pokemon in your lists ? 

1. Pokemon (200+ hours) 

2. Fire Emblem 120+

3.Bravely Default 100+ 

Pokemon White 2: 81 hours
Fire Emblem: Awakening: 80 hours
Animal Crossing: New Leaf: 56 hours
Mario Kart 7: 50 hours
Resident Evil: Revelations: 43 hours
Professor Layton and the Miracle Mask: 27 hours
Professor Layton and the Azran Legacy: 25 hours
Phoenix Wright: Duel Destinies: 13 hours
Kingdom Hearts 3D: 12 hours
Pokemon Y: 12 hours (so far)
Ocarina of Time 3D: 8 hours
DENPA MEN: 7 hours
Dillon's Rolling Western: 5 hours
Harvest Moon: 4 hours
Super Mario 3D Land: 4 hours
Pullblox: 3 hours
Link's Awakening: 2 hours
New Super Mario Bros 2: 2 hours
QIX: 1 hour