I don't know if there is a "most needed" as much as there is desires for certain restaurants our market is lacking. Here are a few ideas:

1.) Lots more of local food movement restaurants (using only local ingredients and changing menu depending on season). Oklahoma is way behind the times with this movement.
2.) A Brasilian Churriscaria (Cafe Do Brasil was in bad location and poorly advertised). I think another one could do well if located properly, planned better and advertised better.
3.) Moto restaurant in Chicago is on the leading edge of edgy restaurant concepts with their edible menu's, liquid nitrogen frozen desserts that look like main courses, custom dinners and more. m o t o | c u i s i n e : 2007
4.) Upscale Cupcake restaurant. See Sprinkles or Kara's
5.) Waterside restaurant on the Oklahoma River
6.) True tapas only bars
7.) Upscale celebrity chef restaurant, Emeril's, Wolfgang Pucks, etc.
8.) Many more full time food vendor carts in downtown
9.) Cuban restaurant