What makes a good game? in your opinion.
I don't really think it's an abstract self-defeating question, I was gonna say it was off-topic and that I would PM the answer, but I'll give a different opinion as to why I don't think Fallout 3 is a good game. It's that it fails in trying to marry up it's themes and narratives with the mechanics.
Fallout 3 takes place in a post apoc wasteland which is not recovering and will die out (yes, I know it's stupid that it's 200 years after bombs fell but that isn't the main point.) All along the way, you meet people who have problems that need solving that, if not solved, may or may not end the lives of all people in towns and even the whole world as presented. That's all fine , desperate people, you want to solve the problems or kill them all (I know there are many examples of where this does not even work either but again I'm skipping major problems here).
Let's talk about the mechanics of how you do that. 1. Combat, the way that you deal with threats in the Wasteland-the major problem of the game-presents no challenge. Apart from Old Olney and some dlc enemies, you tear through enemies so easily that it's laughable. While that gives you the power fantasy feeling, it detracts from the horrible world you are supposed to be in, cause quite frankly, if you can do it, why can't everyone else? Compared to Fallout 1 and 2, where quite a few of the random encounters will spell the death of you, making fast travel a much more tense experience (especially on a first playthrough), these mechanics reinforce the themes of the world and the game far better.
Take a second mechanical point, talking and interacting with characters. If you're gonna have a world where a theme is to decide the fate of the people's you meet, then those people have to be worth saving and helping, or hateful enough to kill. Yes this is a departure from grey morality of the series (which is bad in itself) but they didn't even make the replacement of black and white work either. Nobody you meet is likeable (I didn't even like Moira as some do) which made helping them a real drag. Who cares what Treeminder Birch wants or what his wife (can't even remember the name) wants for Oasis? I'm struggling to remember their personalities apart from what they offer the player in terms of solutions. But, do I hate them and want to kill them cause evil? Not really either. Most of the characters in the game fall under this category, either because of a lack of personality or an absurdity of situation. Take Cantebury Commons. Finding that comic book and letting the antagonizer realise her mistakes might have been a good moment, had you not seen her command (like 3) ants against robots in a town for.... reasons a few minutes earlier, in a supposedly desperate world that you're supposed to take seriously. Compare that to NV, where any faction, major or minor, can garner sympathy or hatred or a varying emotion inbetween (because of morally grey design) for any style of character you want to play.
I could go on and on, but tldr, the game wants you to feel a certain way and to treat the world in a certain way, but cannot get that feeling across if you actually stop and consider what you are actually doing. That makes a bad game. Hope that clears it up.