Fallout 3 is a good,open world action/rpg,plot is interesting enough to keep you entertained.Gameplay is geared towards exploration,levelling up of your character and combat,combat involves a vats targeting system which is great once you get used it.
Graphically very nice but obviously very grey due to the post apocalyptic nature of the game.
I played the game on release and despite enjoying it I haven't returned to it so I can't comment on the expansions and available mods but I can assure you there are numerous of both,definitely worth getting into if you enjoy rpg lite, lengthy and open world exploration gaming. Potentially 100 hrs of gameplay.... +more with expansions.