Should I get them before I start playing the games or are they only good for when I have finished the main game?

I would wait until you've finished the games. The DLC may be a bit cheaper by then.

Well with Fable 2 the idea is that you have the Knothole island as you play through the game, so I would recommend downloading it, as it is quite fun, and does not feel right if you play it afterwards. I cannot comment on Fallout 3 though

Once you reach level 20 in Fallout 3, you'll want to get the Broken Steel DLC; if you don't, any experience you earn will be wasted (Broken Steel unlocks the level cap from 20 to 30).

That being said, I'd probably skip Operation Anchorage and only get The Pitt and Broken Steel, if I had to do it all again.

Why skip Operation Anchorage?

@Frinaldo

I would say wait until you have played the games. It is just a reality of gaming that even the best games have their detractors. In other words you might find that you do not like these games, or you do not feel a pressing need for additional content. So it is better to at least get a good feel for these games before you press onward with added content.

Fallout 3 is a massive game which means even if you enjoy it you stand a good chance of playing the game out. Fable 2 has a quirky style with questionable lasting appeal. Either you cannot get enough of it, or you find yourself tiring of it after thirty or forty hours. So there is no argument for must have.

The reason others will advise against the Anchorage expansion for Fallout 3 is that it is merely a simulation, and thus does not carry over into the main world. Fallout 3 is a real collection game, and some players feel cheated if extra content does not directly result in new gear, new skills, or new locals they can persistently visit.

Though I must say I bothered to review your game list, and frankly there are a lot of things you should probably be picking up first before expansions. You can get new or used full games for the price of this expansion, and their are titles on the arcade that you should enjoy. I notice a number of Rare games in your collection. So perhaps both the banjo games should be worth a look. Along with fan favorites like Mass Effect, Gears of War, Assassins Creed, Bioshock, The Orange Box, Oblivion, and Grand Theft Auto 4.

Basically you are talking to people that have exhausted these great games, and thus are a little pressed for the need to play expansions. Though I doubt anyone would advocate a Fallout 3 expansion over a used copy of Oblivion for twenty dollars. Your not in a position where you need to squeeze value. You can get great value from the hits of the last three years.

Well I'm not sure about the new DLC for Fable 2 as it hasn't been released yet. As for the first DLC pack (Knothole island) I purchased it before I had finished the main game. The good thing about that is that I was able to access new items/weapons, etc. that are only available from the DLC. I used those to help me in the main quest. It's not necessary, but definitely helpful.

I'd wait to see if you actually enjoy playing the game though before deciding to get the DLC pack. I was really having a great time playing Fable 2 and that made me decide to get the DLC pack as early as I did. I'm still playing all the sub-quests even after completing the main quest and DLC quests as well (looking forward to the new DLC as well!)

I don't have Fallout 3 so I can't comment on that.

One quick question, im going to buy an Xbox 360 soon, and im planning to get DLC for both Fable II and Fallout 3. Whats the actual size of those expansions? Cause im going to get an Arcade and just buy 20 GB HDD later (about a month) will there be enoug space?

Well you can always check out

http://marketplace.xbox.com/en-US/default.htm

and if you search for the games you can see the price each DLC as well as the size. For example, the Fable 2 knothole island dlc is 532MB. Fallout 3 the pitt is 492MB, Anchorage is 369MB.

Thanks man, thats less than i thought , 20GB disk will be more then enough, i should be getin a 360 soon.