List any games that you own/have owned for any system that you haven't beaten yet.

NES
Amagon
ExciteBike
Platoon

SNES
Turtles In Time
Maximum Carnage
Separation Anxiety
Street Fighter 2 Turbo
Mortal Kombat 1-3

N64
Wrestlemania 2000
No Mercy
Revenge
Super Smash Bros

Xbox 360
Mortal Kombat (2011)
Metal Gear HD Collection
Ultimate Marvel Vs Capcom 3

Xbox LIVE Arcade
Simpsons Arcade
X-Men
Marvel vs Capcom 2

PC
DC Universe

SNES

Donkey Kong Country (never got 101%)
Donkey Kong Country 2: Diddy's Kong Quest (never got 102%)
Donkey Kong Country 3: Dixie Kong's Double Trouble! (never got 103%)
Super Mario World (never got 100%)
Kirby Super Star (never found all treasures)
Kid Klown in Crazy Chase
Super Star Wars
Super Empire Strikes Back
Super Return of the Jedi

N64

Banjo-Kazooie
Banjo-Tooie
The Legend of Zelda Ocarina of Time (never got all heart pieces, secrets, etc.)
The Legend of Zelda Majora's Mask (same reasons as Ocarina of Time)
Gex 64: Enter The Gecko
Gex 3: Deep Cover Gecko
Rayman 2: The Great Escape
A Bug's Life (didn't collect all coins)

Gamecube

Super Mario Sunshine (never got all Shine Sprites)
The Legend of Zelda The Wind Waker (same reasons as OoT and MM)
Starfox Adventures

Wii

The Legend of Zelda Twilight Princess (same as the other Zelda games)
The Legend of Zelda Skyward Sword (lost interest)
Rayman Origins
Metroid Prime Trilogy (never found all expansions)

Too many to count. My not beaten list is 20X bigger than my beaten list. I am yet to even finish FF VII, VIII (will have done in a few days though), X or XIII. Something always comes up and takes me away from a game for a while and when I come back I just feel like I need to restart and then I just put it off for ages. Continuous cycle.

Well, I haven't finished Robotech Battlecry, despite me saying to myself I would do it one of these days for a few years. I'm so close, I really ought to finish it at least. I haven't finished X-Scape, Pokemon Black 2, and The Legend of Zelda Skyward Sword yet, but i've been playing them off-and-on for some time, so eventually I will.

Well, ones that I own currently but haven't beaten:

Darksiders 1 (currently playing)
Darksiders 2 (JUST ordered online, so obviously haven't beaten)

Lost Odyssey

Kingdoms of Amalur

Well, ones that I own currently but haven't beaten:

Darksiders 1 (currently playing)
Darksiders 2 (JUST ordered online, so obviously haven't beaten)

Lost Odyssey

Kingdoms of Amalur

Well I hope you beat Darksiders 1 before starting 2. Haven't played either. But friends tell me that the first should be completed before going onto the second.

I'll only list my Xbox 360 games, as to list all of them, would take too long

Aliens Colonial Marines
Aliens versus Predator
Assassin's Creed
Assassin's Creed II
Assassin's Creed Brotherhood
Assassin's Creed Revelations
Binary Domain
Borderlands GOTY
Deus Ex Human Revolution
Final Fantasy XI Chains of Promathia
Final Fantasy XI Treasures of Aht Urghan
Final Fantasy XI Wings of the Goddess
First Templar, The
Halo 3 ODST
Spider-man Shattered Dimensions

Final Fantasy: IV (DS)
Kid Icarus (Wii Virtual Console)
Super Mario Bros. (Wii Virtual Console)

*nevermind, some games i only played them for a while, and promptly shelved them into a corresponding section of my collection*

A lot of games.

Ultima 2,Ultima4,ultima underworld, and ultima 7 part 2, the serpent isle.
Wizardry 1
Final fantasy 5
Vampire the masquerade redemption
Dragon age origins
lost odyssey
Paper mario
new super mario brothers wii
Castlevania aria of sorrow
Castlevania 64 2
Metroid prime 3 echoes

I've finished a lot more than i haven't.

Games I don't own anymore:
Psychonauts (PS2)
Wave Race 64
Legend of Zelda: The Wind Waker & Spirit Tracks
Dragon Quest VII-VIII
Parasite Eve 2

Games I own:
999: Nine Hours, Nine Persons, Nine Doors (played through it once but haven't tried to get any other endings)
Again (never made it past that grate puzzle near the end)
Crime Scene (terrible controls make this difficult to pick up again)
Monster Tale
Moon
Okamiden
Crush
James Noir's Hollywood Crimes
Paper Mario: Sticker Star
Professor Layton and the Miracle Mask
Super Mario Land 3D

I really haven't given much time for my games in awhile, and when I do pick them up again it's for a day or two then they're shelved.

I just beat ultima 2.

Can we include post game stuff? If so, here are games that I've started, but haven't completed.

Dark Cloud - I still need to finish the Demon Shaft bonus dungeon floors. I don't remember when I last played it, but I think it was when I recorded and uploaded this (http://www.youtube.com/watch?v=l4Tem4ta47A), which was March 7, 2007.
Kingdom Hearts: Birth by Sleep - I got stuck on Braig with Terra on December 28, 2011 and haven't played since.