I have a buddy coming to town (for Grey Cup) who works live sporting events all over North America. Over the years he's amassed a pretty impressive "been there" list of Diners, Dives & Drive Thru's, though he doesn''t limit himself to greasy spoons. He's also fond of grub that's decidedly non-North American. In short, his list is composed of casual eateries that make you sit up and take notice, either with their atmosphere or menu – preferably both.
A couple of places I've thought of are: Tazza, Blackfoot Truckstop, 1886 Cafe, Lina's Italian Market, The Greek Gas Station/Takeaway on 17th Ave. SW... I'd do a lot better in Edmonton, as I've just been in the Calgary area a couple of years.
He has wheels while in town, but I'm offering bonus points for any place walkable from the Marriott (1st St. and 9th Ave. SE).