Something interesting about Gimli is that it seems every other restaurant offers a mix of Greek with the Icelandic. Although come to think of it there isn't too much that's really Icelandic beyond all the fish, and it's predominantly pickerel which is a Manitoban thing. Universally, I found all the service to be very friendly and approachable.
Country Boy (78 1 Ave)
I think this used to be Diego's Kitchen? Anyhow, this was the most "hole in the wall" of the restaurants visited on this trip. A pickeral platter and a gyro cost $20 and was enough to feed two. Arguably the best bang for the buck for dinner.
Shelley D's (corner of Provincial Trunk Hwy 9 and S Colonization Rd)
Good food and wonderful service from the lovely couple who run the place. Worth the couple minutes drive (or 20 minute walk) to get out there as it's near the edge of Gimli. They are also in the midst of renovating the upstairs into a rentable space/bed & breakfast that I'd highly consider for the future.
Sugar Me Cookie (Unit J - 41 Centre St)
https://www.sugarmecookieboutique.com/Not too expensive, but not what I would call cheap either. There are actually rather limited bakery options in the area, so take what you can get. Worth a visit for the sake of trying it, but this wouldn't be a regular stop for me. The vinetarta is nice, but very expensive.
Beach Boy (70 1 Ave)
One of the larger restaurants, and definitely busier. Better pickeral than Country Boy; not as much fried crunch/texture, but a bit better flavour. Also very generous with their salad sizes. I would pick this over Country Boy, even though it costs a couple bucks more.
Kaffee House (corner of Centre St and 3 Ave)
Cheap breakfast sandwiches/wraps, and really just stick to that. Their other items are pricier and poor value compared to the breakfast items.
Seagulls (10 Centre St)
https://www.lakeviewhotels.com/seagulls-gimli/A bit pricier than the other Gimli offerings, but food quality is a step up as well with many menu items not seen in the other restaurants (let's be real here, all the others have very similar menus). Overall service and appearance is a notch above as well, since this is part of the hotel. Add in the fact that you can have a nice beachfront view from the patio and this is well worth the extra couple bucks.
Whytewold Emporium (190 Gimli Rd, Winnipeg Beach)
http://wwemporium.com/This one was a surprise. Every place we've been to so far has been a relatively older and retrofitted building. This one doesn't look like much from the outside, and it still looks like a hodge podge on the surface, but peek inside and it reveals a rather hefty amount of renovations that have taken place despite the still old fashioned appearance in spots. Anyhow, that's all neither here nor there. This isn't in Gimli, it's off the beaten path in the Winnipeg Beach area and downright tricky to find. They have fantastic wood fired pizza, $29 for the large drunken chicken, comparable to something like a Santa Lucia in the city. Just try it; trust me on that. Apparently they are also famous for their crepes, but I was too full by then to try one.