My BMW F650CS (Teresa - on the left) I use for commuting (~16 miles one way of rural and suburb riding) can pull off up to ~90mpg with massive hypermiling on my usual route
Worse when the weather is cold, of course.
Overall, has quite a good range even with a small (15l - 3.97 US gal) tank
I think that for massive city traffic I'd may choose a lighter (easier to split lanes!) bike with a smaller displacement though, our Hyosung GV250 feels somewhat smoother at stop-and-go and has plenty of power (but isn't ridiculously overpowered) at those speeds (though Teresa can handle it with decent FE too, if I coast/FAS/P&G enough - actually, it doesn't hurt FE at all if I'm up to the mark
).
I'd happily try a Honda CBR125R, for example
Or a 250cc dual sport