I was in LA fairly recently - the vegan food shits on anything over here, but the rest isn't so hot IMO. Had the worst Japanese food of my life there - didn't think it was possible for it to be that bad (had good Japanese too, of course). I thought the Mexican food was mediocre, and we made a point of checking out all the trendiest taco trucks. Last time I went to NYC, was approx equal to London in terms of good food and bad food, but that was forever ago.
Osaka better yes, lived there for a while - still possible to get poor food, but rare. No idea about Australia, as I probably will never go there.
Only places I've ever had consistently good food, and where eating out has been a consistent pleasure, were Japan, Budapest and the countries of the former USSR. SE Asia v decent too, but I don't have much experience.
So I think London is kinda average for European/American cities, albeit with terrible gaps (eg Thai food, as you mentioned upthread). Eating out <<<<<<< home-cooked food, most places in the world. But posh kids have still ruined the experience by making it more pretentious and more expensive for average food.