i played fallout 3 so much i got laid by my ex while i played in an effort to get me off (of the game lol)..... fortunately she failed to break the fallout spell even after getting me laid. last i checked i had about 110 hours and still havent finished lookout or zeta.

Probably 400+. Had about 250 on my 2nd build and have a few since then.
I really liked the game.  I 1530/1550 on 360 and plat on ps3 and am STILL playing the game.

like around 500 or so

About 100 hours and I only had the one character. Still could go back to it and play more too, but I have pretty much done everything and played all the dlc. But I love my character so much that I don't want to start a new one.

On my first playthrough so far - just over 40 hours. Going to start some of the expansions soon.

Just over 60 with 2 characters. That's a damm good game, looking forward to New Vegas this year

50+ hours with most of the stuff done. 

I'm just gonna say "Many"
 
...with a capital M.

I've put over 200 hours like I said before in this thread.

100-ish hours each in two playthroughs. Well, I think it may have been 120 with one, and 80 for the other. 

I'm around 150 hours after all the DLC. 
 
I like that game.

One character, 60 hours for the whole game plus the DLC packs. I basically only played to the complete 1550 gamerscore. I love hunting the land for little stories and buildings, but I was afraid of how much time that would cost me.

all you guys with 100+ hours are fuckin crazy, I'll tell you that. Only 20 hours I believe, already at level 24

More than I feel comfortable admitting.

For Fallout 3 I've probably slapped together a total of about 150 hours on my different characters and I'd do it again in a heartbeat. Can't wait for New Vegas in a few months.

i have around 60+ hours. Man, that game is totally depressing.

I've done around 200-300 that's combining the PC and PS3 versions.

I've platinumed the game so I'm officially done with the game but my last playthrough that I put into the game was 50hrs. But I've played through the game about six times so easily 120+. 

5. but i just got the game :P 
purchased it just a few nights ago

I think I beat it with a little over 20 hrs then I returned it which is more than what i did with oblivion which was like 30 minutes, I really should have given that game a second chance.

PC: 60 hours 
Xbox 360: 34 hours  
 
Both versions completed and with the DLC.

A serendipity 115 hours.

140 without DLC. Isn't that game great, it is a  scientific breakthrough.

Probably about 120. Loved that game. 
 
Shit, I want to find my disc, and play it now :/

Probably around 80 I've payed almost every disc mission and 3/5 of the dlc missions. I love the game, but I only played through with one character.

A whole lot of hours, finishing it first on 360, then finishing it on PC and burned through 4/5 of the DLC missions.The pitts left to finish.

I have so far put 75 hours into the game. I would like to put more into it, but now it refuses to start. Great stuff, I just wish I could keep playing.

Last night I saved and noticed I was up to 114 hours. Still got a bunch to go, too.

Highest amount of time for one save is 84 hours. 
Total of all my saves would be around 135 hours.

" about 13 hours, got bored, traded it in, never bothered to finish it. what a bore. "

I put in somewhere in the 80-hour range.  Played the main game and all the DLC.  Lot's of fun, but man I'm tapped out until New Vegas.

I don't have the game anymore, but I estimate about 40 or 50 hours.

Around 100 hours, between two characters. With the first character I did almost everything (including the DLC packs) and with the second I'm only at the beginning (around level 8 or so).

~200.

At least somewhere around 200 hours. My original character is sitting at 135-ish and I've made countless new ones.

I recently got back into it (I uninstalled it a while back) and on my only character I'm about 30 hours in. Haven't completed that much of the main quests, but I did do Point Anchorage to get the armor. Really, I'll just go in and explore the wasteland or do a couple quests (not many are actual plotline ones) and then get off. Been playing about 3 days so far.

About 220 Hours across 3 characters (Evil, Neutral, Good) lol. I still play the game all the time, I bought it the first day it came out.

Um. About 29 hours. A level 10 Ne'er-do-well (that's slang for awesome, I'm told).

I've made 4 or 5 characters, and last I checked (6 months ago) it added up to about 385 hours.  This game is awesome, and I can hardly wait for New Vegas.  I may buy several different copies, just to have all the wonderful accoutrements that will come with.  And yes, that was me trying to be a sesquipedalian.

128 hours, with 64 of them on my first character. I never bought any DLC.

I finished the game with 17 hours on one character and never picked it up again.

500+

around 10 before I got tired of the combat.

One or two hours. Got bored once I got out of the Vault.

About 300 overall across various saves both on 360 and on PC, but mainly on PC. Mods make the game so much more fun.

Still on my first and only character.
 
I think I'm at about 52 hours?  That's also with the Broken Steel and Point Lookout DLC.

I've got just over a day of playtime on my first and only character.