@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.







