Being from Ontario but living the last 25 years in Alberta and BC, I've done the trip many times. I'll give you my not-so-short list of highly recommended destinations at least on the Canadian side. Some of these will be maybe an hour max off the beaten path (a.k.a. The Highway), so do some googling and see if you think they are worth the detour based on your own interests.
1. I'm from the Sudbury Area, so I always recommend the Big Nickle Mine or Science North and Ramsay Lake for first time visitors. If you have been deep underground inside a mine before, or not into the geology of the North and some general science center type exhibits, it's not necessarily a must see, but cool.
2. Sault Ste. Marie - You can google the local sites, but on the way home, consider Mackinac Island on the US side. Big old fort and isolated Victorian town on a "no-car" pedestrian island. Did it as a family vacation in my youth, and it was very cool and memorable.
3. Wawa - Go right into town for lunch or coffee and see the original Wawa goose (not just the highway one), and some trading posts and local shops. This is the gateway to the north side of Superior, and one of my favorite Ontario drives. The very north end from Marathon to Thunder Bay is amazing. Plan to stop for pictures a lot, lol Maybe hit the Ouimet Canyon/Eagle Canyon as you approach Thunder Bay if you are interested.
4. Thunder Bay - Head downtown and check out the water front. The sleeping giant is viewable from there and Isle Royal is a cool park, but actually involves a maritime border crossing to the US side. Fort William in town is cool, and definitely hit Kakabeka Falls on the west side as you leave town. There is camping there if you are looking to do that.
5. There is a giant moose sculpture along the highway in Dryden along the lines of the Wawa Goose, and Kenora has a cool museum on the north and the lake of the woods area. A nice stretch break.
6. Winnipeg - Go downtown, and check out the forks market at the confluence of the rivers. The old Fort Garry Hotel is worth the big money IMHO if you feel like splurging on a night (old building is coolest). There is a rotating restaurant atop the new wing which would be a hit with the wife for sure. Sunset dinner up there is absolutely divine. You can google the rest of the cities attractions, and decide what hits your interests.
7. Saskatchewan - People who blast through Sask are fools. FOOLS I SAY! It holds many little gems worth the side trips, and it's not all "flat" off the highway. You can bypass Regina too easily, but the RCMP Heritage center is worth the break, especially if they are doing drills with the RCMP cadets.
8. Pick a site or two in Sask based on your interests, but they are all an hour off the highway, so doing them takes a little time. My top two are the Great Sandhills/Leader and Cypress Hills. Did you know there is a big white giant sand dune desert in the middle of Saskatchewan? Most don't because they think it's all farms and are too lazy to get off the highway, lol. There is a cool museum, and then go play in the dunes and feel like you are in the Sahara. Leader Saskatchewan is a Hutterite colony, and has interpretive sites and the amazing history of these folks and this beautiful province.
9. Cypress Hills Park is absolutely gorgeous, especially in the evening and around sunset. And they are not flat! Riding heaven. You'll also hit the salt flats in Chaplin on the highway on the way. Plan to stop and check them out.
10. Moose Jaw and Swift Current have beautiful downtowns if you want to stretch and explore.
11. Alberta holds a lot to see, so you'll have to pick a couple. If you are there around mid July, Calgary Stampede is a must (if you are a country music fan, this is a mini mecca). This city lives for it. Locals love it or hate it, but it is an amazing event. Calgary also has a cool downtown, Stephen Ave, and there is the Calgary Tower too.
12. Get to the badlands in Drumheller and do the Dinosaur museum and explore the park. Don't argue, just do it! lol
13. You'll hit the parks on the way west. My Home. Plan a few days, and Kananaskis is cool, but my top five are: 1- Banff (Duh! Ride the gondola, and consider the dinner package up top - great deal) Plan a full day! 2- Lake Louise (Again, Duh! Plan a half day and go up to the Chateau, the ski hill (another gondola if you want), and Moraine Lake. Lake agnes tea hut is amazing if you have time for a short hike (1hr round trip with a snack up there). Stay there or the Banff Springs if you have the budget. It's only money right? 3- Johnston Canyon, and do the hike. Amazing and easy/quick. The campsite right at the canyon has amazing little cabins you can rent too. 4- Jasper Parkway, DO IT! Seriously, the greatest ride in all of Canada! Life Changing! Stop at the Icefields interpretive center, and if you have the time and budget take the big monster bus onto the glacier, and optionally do the skywalk.
5- Jasper, and the Jasper Park Lodge. Mt Robson and Maligne Lake are cool side trips if you have time. There is another gondola, and so many things to see up here, it's endless and a little overwhelming.
14. The trans canada is the popular way though BC, and I can't discourage that for time alone. Roger's Pass and Revelstoke is very cool, with many sites on the way. The south route across the province adds 4-6 hours at least and you can't do the Cache Creek to Pemberton route. A favorite of mine. The freeway from Kamloops to Hope is nice, but nothing compared to the long way round through Lillooet and Whistler too. Peak to Peak Gondola! Google that!
15. Consider a side trip day down the Okanagan Valley. Kelowna, Pentiction, and Oliver/Osoyoos are all cool and very unique wine country and desert climate.
16. Vancouver, go downtown to Gastown/Robson Ave/Granville Island, and hit Stanley Park for the afternoon too. Lots to see and do. Cool city, and the polar opposite of Toronto in so many ways.
17. Island treats include Downtown Victoria Waterfront/Empress Hotel, Malahat and Goldstream Park, The whole highway north, and all the little island towns. Nainaimo, Parksville, Coombs for sure, and Tofino if you have time. Amazing Ride! All the way up to Campbell river along the water is full of cool towns (avoid the freeway unless you want to make time back down again), and Qualicum Beach, Fanny Bay (mecca for oysters), Courtney Comox, etc. The extreme north end of the island is remote, but amazing. I'll post a link at the end to another site where I posted a trip up there this summer.
18. If you get onto van isle by the Lions Bay/Nanaimo route, consider the Swartz Bay/Tsawwassen route off (it's longer, but the better sail anyway), or if you want to skip into the USA directly, the Port Angeles Ferry from Victoria direct is great on the bike, or there are option direct to Seattle.
19. Speaking of Seattle. SEATTLE! Awesome City! Do the Rock & Roll hall of fame/Art Museum/Space Needle all together, and then go downtown to Pike Market, the water front, and the underground tour. Baseball and Football stadiums are right there too if you are inclined. Great small old-school feeling ballpark if the Mariners are playing. Optionally, the Boeing Factory tour and the Museum of Flight are personal favorites on the south end of the city. Plan a half day or more if you want to hit them both.
19. The route from Seattle to Spokane is beautiful and lots of cool towns along the way. Decide whether you want to go south to do things like Yellowstone, Mt Rushmore, or north and hit Glacier Park (Going to the Sun Road!), in which case I recommend considering route 2 through Shelby to Grand Forks and Duluth, and the small towns instead of the freeway. Cool, cool, cool, and a better example of real rural America IMHO. But lots to see either way. I'm still enjoying exploring the US side myself.
Check out some BC parks and Van island ride reports I have done here if you are interested.
Riding the Canadian Rockies and Beyond... | Adventure Rider