Extraction Poiint is the best, and Perseus Mandate is a great adition too.
F.E.A.R. FILES is a package of 2 EXPANSION PACKS, so don't expect a new graphics engine or a 100% new stroyline, the game looks great and plays the same, it has a few new additions, 2 more weapons in Extraction Point and 2 more in Perseus mandate and much more enemies, in Perseus Mandate there's also a whole new faction and they are tough to fight with.
F.E.A.R. would be incomplete without Extraction Point, because it adds more to the storyline and it is more creepy than the original one, Perseus Mandate is also great, even if many people don't think it is, and both games are very very hard, that's good because today you can finish most games in about 4 or 5 hours.
Perseus Mandate has some of the most scary moments in the saga and it has more variety, there's still offices and labs but now there are caves, streests and even levels in daylight.
The new weapons are awesome and the new enemies are even scary, you have to play this game before you play Project Origin, that way you'll understand many things about the storyline of the saga.
This package is one of the best deals you'll find, you won't regret it.