I am not from Chicago, but I enjoy eating in the city. My wife and I like:
My Wife likes MArche, I have never been there.
and Bistro 110.
The Saloon is a steak house that is not stuffy and has a jazzy atmosphere.
Red Light offers a great tasting menu where Chef Chen actually will bring the items to your table. She creates what she desires, as long as you do not have an aversion or alergie to something. It was one of the greatest meals I ever had.
Red Light is the only resteraunt that I have ever been to, where the waiter try to down sell my on Champagne. I wanted a $90 bottle of Veve and he convoinced me a $39 was better, and I beleive he was correct.
Working north from the river, here's some suggestions:
Tizi Melloul (River North)--modern take on North African
Kamihachi (Old Towne: Wells S. of North)--solid sushi/sashimi/great little upstairs bar
Twin Anchors (Old Town/Lincoln Park: Sedgewick N. of North)--old school Chicago i.e. ribs, Old Style and tons of atmosphere...it was one of Sinatra's main haunts when in town.
Landmark (Lincoln Park: Halstead & North)--very good food, loud, high energy, shallow broads might be impressed but they also might leave with a drunken commodities trader
Eonoteca Piattini (Lincoln Park: Webster & Sheffield)--great neighborhood place, great wine list and food, not terribly romantic but you'll show your date that you know the cool off the map places (i.e. the opposite of Landmark)
Merlo (Lincoln Park: Lincoln north of Wrightwood)--storefront Northern Italian. Some say it's the best Italian in town. Somewhat expensive but worth it. The storefront atmosphere makes it non-intimidating for a first date, but if that first date is a foodie she'll definately appreciate you knowing about the place. Plus, Delilah's the best whiskey bar in America is 1/2 a block up Lincoln for an after dinner drink.
In Lincoln Park, how about Sausalito on Diversey. It has the added advantage of alot of other bars and coffee shops that you could stroll to if you want to keep the date rolling. If you're looking for a bit more "haute" in your cuisine, then Riccardo Trattoria on Clark or Erwin on Halsted would be good.
In Old Town there's Cafe Adobo for Mexican or Ristorante Dinotto, both good quality and good date vibe. Nearby Topo Gigio is okay for italian though I like Dinotto more. Again, there's a fair number of places to stroll to near all of these.
Over on Halsted I really like Vinci as a date destination.
Further south, you get into Rush Triangle and River North and there's just dozens of options.
re: Chicago Mike
I like the idea of the Wells Street area - Old Town. Lots of variety and a nice palce to walk around after dinner. Personally, I prefer Topo Gigio to Dinotto, but maybe a matter of taste. Adobo Grill is also fun. Or Kamehachi for sushi which is also mentioned below.
After dinner, its a nice place to walk around. You can always be yuppies and hang out at the enormous Starbucks at Wells and North. Its packed unitl late at night, plus I have a soft spot for Starbucks because its where I met my wife, as embarassing as that may sound. And yes we HAVE seen "Best in Show" for anyone who is wondering.