Fallout 3 is a dull and completely broken RPG, taking place in a nonsensical, brown-'n-bloom world designed like an amusement park, with a vapid story and terrible characters. Oh, and it's buggy as hell, with every single save in the PS3 version becoming unplayable eventually.

I could go into more detail, but there are better, more in-depth takedowns of the game around the internet, such as this one by hbomberguy. If you never played a Fallout game before, just forget this exists and play New Vegas instead -- that's an actual RPG, not this.