I'm giving it 5 stars but it doesn't mean it's absolutely perfect. The show gets substantially better after episodes 3 and 4. The first 2 are slightly clumsy. They have all things considered done and amazing job making a show that is both true to the franchise but unique (for the most part).
The review below does contain a few spoilers so please, if you have intentions of watching the show, stop reading this review.
As a self confessed mega fan of the games, the first 13 minutes of episode 1 nearly made me switch off. 3 very lazy and clumsily placed incest jokes got us off to a very poor start.
Fallout as a franchise is full of what some would call alternative or dark humour often inappropriate and that's it's core charm.
The jokes mentioned before feel shoehorned and even the actors seem uncomfortable making them.
*Spoilers*
There are a few inconsistencies at the start but they are setting the scene for new audiences who maybe haven't played the games.
For example, when Lucy gets married and realises her new husband isn't a vault dweller, she identifies him and the other guests as "raiders". I don't understand how she could have made that identification when, at this stage, she is both unaware that reclamation day has already happened without her vault and that the only interaction vault 33 has is with 32 and those that leave 31 to join 33.
They added traits to some factions. The brotherhood of steel for example seems more focused on traditions like branding which is not mentioned in the games.
The fiends are explicitly all cannibals according to maximus when only cook cook was designated a cannibal in New Vegas but this could also be a regional thing.
Ghoulification via drugs is also a new addition.
A very enjoyable interpretation of the fallout universe that is both unique and engaging once you get past the cringe incest and sex parts that absolutely were not necessary in any way.