Ooh! Me! Me! I've bought the Commander Pack a few times to get friends to try out Total Annihilation. I also got SupCom and Forged Alliance which are great fun, but I find FA a little stuttery on my machine.
I saw Total Annihilation in a newly designed box at FutureShop the other day. Looks like they're keeping it alive, which is good. They should have made a deal with GOG.com though, that would have been a super addition.

I'm rubbish at SupCom against real humans. Nonetheless, let's just say if SupCom were available when I was in university, I'd not have graduated.

I ghost the old Thief games, which is playing them through without being spotted (in the game mind you, people see can me playing them)

my gaming obsession revolves around old-school MUD/MOO's, which are basically text-only multiplayer games. i've been making my own for about 9 years now, and have been playing them for about 15. nothing more true than the old catchphrase that they feature the most advanced graphics ever: your imagination.

My biggest gaming obsession:
1. Finishing games. I will play a game constantly, no matter how long it takes, no matter how many other new ones are bought, I won't stop until they are finished.
A sense of completeness.

Oh the shame. I only own the bugger as well. :)

@BoxOfSnoo:
nice! have you tried TA in mp with unit packs like UTASP? And do you know of TASpring ?:) FA rulez, it just needs a mod that will recreate original TA in FA engine :)
@AngelKnight:
you'll get better :) , i'm no master myself, but I can play this forever. It just won't let me go, certainly not until I get nuked :D

My gaming obsession?
Good, atmospheric RPGs with a lot of choices, good story and romance in it.
This combination is my killer and that kind of games is whispering to me years after playing them.
Oh and of course my protective nature when it comes to older games. I would not have any problem to try beat (in case I would feel stronger than the other guy, else - or in case the victim was girl - I would try to hurt him/her some other way, for example spreading gossip about some nasty disease he/she has) someone who si mocking old game just because the game its old.

RPGs of all shapes and sizes.
...not to say my friends and cousin don't get Fable, or Mass Effect, the newest Final Fantasy or console/PC game by Bioware or Bethesda, it's just that I go nuts.
I have NES version of FF1, both the SNES and GBA versions of FF4 and 6, along with FF4 for DS, every Mario RPG, Earthbound, Chrono Trigger for the SNES (and soon, for the DS [I CAN'T HELP MYSELF!]) Brain Lord, BoF 1&2, BG 1 & 2 plus xpacs, every game made by Troika, The Witcher, Oblivion, Jade Empire, Mass Effect, Skies of Arcadia for Gamecube *breathes* PSO for Gamecube (with no interenet access, but I don't care![HELP ME]) Tales of Symphonia, Secret of Mana and Secret of Evermore, KOTOR 1 and 2, Fable, NWN 1 and 2 with all xpacs, Final Fantasy Tatics Advance and Final Fantasy Tactis A2, Gladius, Freedom Force, AND Penny Arcade's On the Rain-Slick Precipice of Darkness, Episode 1! *gasps*
Of course, that's not including the Action RPGs Like Diablo 1 and 2, Titan Quest, Nox, and Hellgate London, or any MMOs I am currently playing or have played like SWG, WoW, WAR, and Pirates of the Burning Sea, nor the RPGs I'm playing off of Gametap or plan on getting with GoG once I'm done with the games on Gametap, like the Phatasy Star series, Fallout Series, Sacred, and most likley whatever good RPGs that are on there that I haven't found yet.
I have avoided buying Tales of Vesperia and Lost Oddessy out of sheer force of will (Rented Blue Dragon, not really fond of it), and will likely fail, after all the cash I get for Christmas comes in. The trouble of finding older RPGs is all that keeps me from Lufia 1 and 2, which I rented when I was young and enjoyed quite a bit.
...It is also the main reason I have never owned a Playstation, because if I did, I'd go broke buying all the great PS1 and PS2 RPG series and stand alone titles, just so I can play them all.
Edit: forgot a few :p
Edit2: there are others, but I'm not listing them because, I don't want to search for them for the next 30 minutes just so I can get their names right. Or it's Lunar: Dragon Song which I regret ever getting...

CAVE STORY!
Dear God, I loved that game so much.

I was completely obsessed with the first Baldur's Gate. I would play for 17-18 hours straight on a Saturday and my husband almost divorced me because of it.
I replayed it many times but I've had to be very careful about limiting the time I spend playing. My husband plays some games, but is NOT a gamer.

yay! Though I don't have the skill to finish every of them :)
One big obsession of mine is playing the game the most finalized as possible. I CAN'T play anymore at Oblivion because of all the patches and 3rd party gameplay add-ons. Not forgetting the textures packs, models packs... I can't decide so it drives me crazy :(
Something else: I LOVE single player mods. Of any kind: new scenario or total conversion, I GRAB!
I had an obsession once, finishing the Myst serie. It was so huge that I just "had the eyes bigger than the stomach"...

The original Pizza Tycoon is my obsession...
It was great... trading weapons to make money, building your restaurant, making pizzas, entering competitions... Just loved it..
Unfortunately every single update that was made sucked... Pizza Syndicate etc just never captured the originals charm...
I wish someone could remake the same game but for todays technology

I think it's Yu-gi-oh games... I love (trading) card games.