There's quite a few good eats to be found in Grand Forks actually. I would skip the sushi... but if you've never had it before you'll be fine, so go for Konechiwas. I've moved away from ole GF, but I think these restaurants are still in town.
The best burger in town, by far, without a doubt, can be found at "The Hub", which is a bar. I'm not sure of the age limitations, but it's amazing. The Hub burger can bring tears to a grown man's eyes. [The Hub is located on N. 3rd, kiddy corner from the Toasted Frog]
The best (and most interesting/varied) food in town is found at the Parrot's Cay, also a bar. The cooks have some lateral influence as to what they cook each month, so the "Cook's Special" will change month to month; I've had an amazing shephard's pie there, as well as some incredible creole/cajun food. Chicken strips kick ass, and if you ask for hot wings, get the 13s. You get a shirt if you eat the whole dozen. 21+ only. Sorry kiddies! [The Parrot's Cay is located in the same building as the Valley Dairy WAAAY south on Washington. Near Landeco Lane if that helps at all]
I know this next one is very contestable for some people, but for my money you just CANNOT beat Shangri-La for asian cuisine. I live in Massachusetts now, and I --still-- crave their eggrolls (handmade at the restaurant) and their curry beef (stunningly good). This is a family owned establishment; it was passed down from the current owners' grandparents who opened it. If you haven't been there I HIGHLY suggest it. The consumme soup is still, to this day, the best I've ever had. All ages. [Found in the same strip mall thingy as the DownUNDer. It's on 42nd street, near the Dakota Bookstore and Red Pepper].
Speaking of which, I've heard the Red Pepper's quality has gone down, but that matters very little: The RP is a Grand Forks/UND institution. Eat there or forever feel ashamed.
For good diner food you can go to the I29 (found on... Interstate 29) but I prefer the Emerald Grill, which is off Gateway, near the Perkins.
Best pizza is found at the Mike's Pizza, a little joint directly next to Whitey's in East Grand Forks. I wouldn't order it for delivery (it's a bit pricey) but the sauce and crust are absolutely awesome, and if you're 21+ (or have a convincing fake) they have a $5 minipizza/beer special. Great value. All ages, 21+ to drink/sit at the bar.
OK. The greatest secret while I was at UND was the little cafe found in the basement of the Museum of Art on campus (I'm serious). I've heard they may have changed their menu..? But last year it was amazing food, interesting, often organic, and very, VERY reasonably priced. I think they only do lunch, but it's well worth your time. The place will be packed with professors and students. Do it, it's great. Order the hummus [Across the parking lot from Twamley]
Mexican food: Stay away from La Campana/Paradiso and Mexican Village. Paradiso is overpriced and the food is microwaved (the margaritas are good though, so if you want to just eat chips and get drunk... well it's pretty good for that). Mexican Village is VERY unpredictable. Sometimes the food is adequate, or even slightly above average, but sometimes its so cold, recooked, and disgusting as to be mildly frightening. The best mexican food available in GF, I would say, is the little mexican place that is in East Grand Forks just a little past Cabelas. I can't remember the name, but it's pretty tasty, the food always seemed fresh cooked, and the portions are hefty.
There are tons of other places to eat: Whitey's, Sander's, Toasted Frog, et al., but the above are probably my favorite places to eat that are distinct. Whitey's is awesome, but it's just traditional american cuisine.
Eat, Drink ... and be Merry!
fuz