Latin fusion (Carnivale)
Jewish deli (Steve's Deli)
Turk (Turquoise Cafe)
Cajun/creole (Heaven on Seven)
Argentine (Tango Sur)
Tapas (Cafe Iberico)
Afghan (Kabul House)
If I had to choose just one of these places, I'd go to Kabul House in Skokie. The food is very good and really different from what you find elsewhere, it's not expensive, and most people probably haven't been there (or even heard of it).
I second Greektown, but prefer the Parthenon (I think it's more authentic).
For Middle Eastern I'd recommend Semiramis or Noon-o-Kebob, just a couple of blocks apart.
Good Ethiopian suggestions.
Try Taste of Peru for amazing South American fare.
4639 N Kedzie Ave, Chicago, IL 60625
Taste of Peru
6545 N Clark St, Chicago, IL 60626
Noon O Kabab
4661 N Kedzie Ave, Chicago, IL 60625
Parthenon Restaurant and Banquets
314 S Halsted St, Chicago, IL 60661