The general standard is very high, though trying to chase after “the best place” does not seem worth the effort — it is more about choosing the best dish to order. As in India, the hotel restaurants are excellent, and you can sample everything you might want without leaving a single restaurant, if you find the dust and heat too daunting (I do not, but you might, please do believe me on that one). The crowning glories in Karachi are the biryanis and the lassi. A randomly chosen lassi here seems to match the very best Indian lassis in quality. The karahi dishes come alive like nowhere else. Qorma sauces too. Vegetables are hard to come by, especially greens — the restaurant version of Karachi cuisine is quite meat-heavy, and the overall selection of dishes is not so different from what you find in the Pakistani restaurants in Springfield, Virginia. That said, the greens and herbs that accompany the meat dishes are fresh and vibrant.
One secondary consequence of the meat emphasis is that Karachi Western fast food is much more like the Western version than you might find in India. Hamburgers carry over very well to the Pakistani context, as does slopping together meat and bread in various ways, a’ la Subway. There is Movenpick chocolate ice cream in various shopping malls and hotels. Reasonable Chinese food can be found, can you say “One Belt, One Road”?
Golub Jamun, typically an atrocity in the United States, is marvelous in Pakistan.