Since the good points have already been detailed over and over in the above reviews(re: the "S.P.E.C.I.A.L." system, fun setting, great cut-scenes etc.), I will focus on what Fallout did NOT get right(which is very few things).
For starters, R.P.C.s(Recruitable Player Characters)/party members. FO tried to get 'artsy' or something wo rather than simply allowing you to control the other PCs in your party, the developers opted for this element to be left to the A.I.. The result is that taking along ANY other characters is a big time disadvantage for you and no fun at all. Your party members will repeatedly shoot you in teh back and/or try their damndest to get themselves shot in the face amongst other nasty quirks. If you do not recruit any other party members then you will have a near-perfect experience.
Also, in regards to having other party members, you will be dealing with the convoluted inventory system. Why on earth did they feel the need to make the inventory management so BAD?! I can understand wanting to try something different than what most other RPGs were doing but this aspect should have been jettisoned during beta testing! You cannot simply trade items between characters and choose who uses what and how. It is just a mess all around.
Other than that the game is absolutely marvelous!