Minecraft (I don't know how much exactly, but I think it's atleast 400 hours)
Team Fortress 2 (300-400 hours)
Skyrim ( 275+)
Dark Souls (250+)
Super Smash Bros Brawl. (200+ For me. Total: 730+)

The games that I've spent the most time on:

1.) Super Smash Bros. Brawl- 1000+ Hours
2.) Dragon Quest VIII- 300 Hours
3.) Super Mario 3D Land- 200 Hours
4.) Pokemon Black/White- 200 Hours

Other Programs on my 3DS

1.) Internet- 1000+ Hours (That's sad) I've been on the internet more on my 3DS than any other game.
2.) 3DS Sound- 300+ Hours(Also sad)

I play video games alot but not that much.:D

I'm not going to bother to look up the hours played, but my list looks something like:

1. Super Smash Bros. Melee
2. Super Smash Bros. Brawl
3. Pokémon Ruby

Fire Emblem: Awakening's on its way toward catching up to Pokémon, though. . .

Dont know the exact hours but

Gears of War - 600
Call of Duty 4 - 500
Halo 3 - 300

Mario Kart Wii is about 1000 hours, but Roller Coaster Tycoon may be more. I'm not sure.

Over 8,500 hours in Runescape when I was younger...

More recently, I have Dota 2 and Battlefield 3.

Origin says I've played 60 hours of BF3, but that doesn't feel right. It feels like I've spent over 200 hours easily.. O.o

324 hours played in Dota 2.

Final Fantasy X - 250 hours

Cod WaW - 200 hours

Castlevania Harmony of Despair - 120 hours

Fallout 3 - 150 hours

Legend of Dragoon - 100 hours

Monster Hunter Tri with 105 hours
TF 2 with 109 hours 
Dota 2 with 186 hours

These are all my estimates, but they are probably fairly close:

SNES: Super Mario World (~10 hours)
N64: Super Smash Bros (~300 hours)
GCN: SSB: Melee (~500 hours)
Wii: SSB: Brawl (~300 hours)
Wii U: NSMB: U (~5 hours)

PS2: GTA: San Andreas (~50 hours)
PS3: Black Ops (~100 hours)

GBC: Pokemon Silver (~200 hours)
GBA: Pokemon Ruby (~150 hours)
DS: Pokemon Diamond (~100 hours)
3DS: Zelda OoT (~35 hours)