If you're going to pitch Buffalo, I'll add Rochester. Both get a bad rap because of snow without skiing, but, yes, there's lots to like for those who live there or visit.
Queens, in particular, is underrated. If the path along (or beneath) the 7 train out to Flushing isn't the most ethnically diverse place on the planet any longer, it's still in the top 5.
@karstenkibbe, you might as well add Douglaston to Jamaica Estates and Forest Hills Gardens, and then properly consider them a component of the borough's staggering variety of cultures, from the north to south shore.
North Stamford, in parts, is indistinguishable from back country Greenwich and New Canaan.
One thing that has genuinely distinguished Stamford from other CT cities is that it united what we're once separate places into a unified city even before the redeveloped downtown that has been mentioned. As pointed out elsewhere, many US cities have done similarly, annexing adjacent towns and even entire counties (like done or all of Louisville, Columbus, San Antonio, and Indianapolis have), and become healthier for it.
Someone similarly noted that West Hartford, Glastonbury would be interesting, wealthy, tax-revenue contributing neighborhoods in such metropolitanized cities, but Conbecticut's cities suffer in part because only in Stamford do the wealthy and poor have to share resources & responsibilities. Stamford also hugely benefitted from CT's more attractive tax structure when major corporations departed from NYC a half century ago.