Darn, I looked this up before I read your details.
http://www.topofthemark.com/

It depends, but to start with: Delfina (18th @ Guerrero) is a favorite of my most critical foodie friend; Incanto (...somewhere in Noe Valley) is also great for omnivores. Bar Tartine (19th @ Valencia) is a little pricey but very good. These may all be a little fancypants though. Some guidelines regarding price, cuisine, neighborhood, etc would help guide you to a better suggestion.

I’m a fan of Zazie in Cole Valley: French, good food, reasonable, and great ambiance.

Hey Ben, Zazie does have great ambiance, I agree, but I’ve eaten there many times, and found that the dinner menu is nothing compared to brunch. An alternative Cole Valley hot spot would be Eos Wine Bar. It is dark, mysterious, serves tapas style food and great wines. You can’t go wrong there.

I second nikipedia’s suggestion for Delfina, and the best part is that you don’t even need a reservation if it is just 2 people. You can walk in and sit at the bar, or along a designated area that overlooks the whole restaurant. My wife and I love going there on our rare “date nights”.

Eat out in the Richmond for great food AND parking.

Aziza Geary @ 23rd-Moroccan/Mediterranean. I usually have one of the lamb dishes because good lamb takes too long @ home and I love lamb. Friends tell me the bar is great… Nice ambiance and menu but tempered by the Mediterranean influence. No belly dancers or sitting on the floor or touristy stuff.

Chapeau-Clemeni @ 15th-French so a little formal but cozy and great service. Very nice gourmet meal, definitely a cut above. A great place if you have a play or concert to go to. Between 5–6 a stupendous prixe fixe $20 meal worth 3 times thai. Love the goat cheeze appetizer and soups (well almost every dish) stands out.

Pacific Café-Geary @ 34th-Loving the fish but hating the wharf? Great, freshest seafood including lick the bowl clam chowder. This one is walking distance so we are there a couple times a month.

Mayflower-Geary @ 27th I have only been here for banquets because it is a little pricey. That is still less than $30 ea on the menu. Favorite dish walnuts and prawns. Sometimes a little busy because they do great banquets so we like Ton Kiang Geary abt 24th? for great dim sum

The Front Porch in The Mission is a really cute place. I went there with a group but saw some couples on what looked like first dates. It’s like upscale soul food. Delicious!

I always liked the Blue Light Cafe; not sure if its still owned by Boz Scaggs or not. It used to favor his own fried chicken recipe. Comfortable place. If you like something a little different and perhaps eclectic, try Betelnut on Union St. I liked the way they serve sake, and the food was excellent.

Two more recommendations for date places:
The Citrus Club: cheap and delicious noodle soups in the Upper Haight.
Emma’s Spaghetti Shack: Tasty, hipster spaghetti in the Mission.

also, see
http://www.fluther.com/disc/2069/what-is-a-great-date-restaurant-in-san-francisco/
(among others)

I would add (for something very different than the Mission suggestions – I don’t know your style or what kind of date you’re aiming for):
~ Greens at Fort Mason – nicer, gorgeous view, amazing local veggie food – and pretty parks to walk in nearby (sunset, anyone?)

also, in the Mission you can hit Dolores Park for a pre- or post-dinner stroll

@ben—- the citrus club is also a great place to break up with a girl. My old roommate dumped several ladies there including a friend of mine : ) For that reason, I will never accept a date to the citrus club!!!!

If we’re talking vegetarian, try Alive! on the 1900 block of Lombard.

@ben: I GA’d you even though it’s EmmY’s Spaghetti Shack. That place is the best.

Nopa…No doubt. Nopa