1) If you’re mainly looking for something believable, most major U.S. cities use one of the following:

• Surnames of VIPs, usually explorers, founders and national political leaders (e.g. Houston, Columbus, Washington, Pittsburgh, and Jacksonville).
• Anglicized spellings of Native American terms, usually related to geography. E.g. Shikako (“skunk place”) -> Chicago and Myaamia (“downstream people”) -> Miami.
• Southwestern cities usually use Spanish terms, usually San/Santa + Spanish name or Los/Las/El/La + Spanish term (e.g. San Jose, Los Angeles, and El Paso).
• Some cities settled by the French use French terms (e.g. Detroit / “strait” and Baton Rouge / “red stick”), are named after French places (e.g. New Orleans) or French saints (e.g. St. Louis).
• Some cities settled by the English are named after English cities (e.g. Boston and New Amsterdam getting renamed to New York).

2) If you’re looking for something more exotic and/or more thematic, I’d recommend starting with a syllable that has the right sound/feel and then adding suffixes from there. E.g. if I were trying to name a city that was economically wrecked and high-crime, I might start with a syllable like Bent or Pac or Mar, and then add a suffix (don, ion, ola/oma, burn, dere, atur, ville, port, er, burg, boro, rst, oma, sen, iet or whatever suits you). In this case, maybe Marburn or Bensen or Paccola.

3) Unless you’re going for a very “comic booky” feel, I recommend against combining an English adjective/noun and “City”. For example, names like “Central City” and “Star City” tend to be very generic and don’t sound like actual names. (Of the 100 largest U.S. cities, only 4 end in “City” and only 7 use a common English word besides a surname: New York City, Oklahoma City, Kansas City, Jersey City, Aurora, Phoenix, and New Orleans).