The Intercontinental Hotel on Front St. I always enjoyed it the 3 or 4 times I was there but it had another name back then. L'hotel I think. I even made a point of going in when I wasn't staying there. Great location for accessing transit and within walking distance of the big tourist spots. Close the St Lawrence market area as well which is always interesting.

The Sutton Place Hotel is pretty good and so is the The Park hotel on Avenue road. Both have easy access to transit as well.

The most venerable hotel is the Royal York. It's Landmark for torontonians. I've never stayed there though. I have passed through it or attended meetings on the surface it looked pretty first rate.

Stayed at the Harbourfront Westin last year. Wasn't impressed at all. I think I expected to much and the disappointment left a bad taste.

All of those first 4 are close to the underground pedestrian mall, a North American phenomenon for dealing with the winter weather or inclement weather. It's really just an underground mall stretching for a few miles. It's heck during morning/evening rush hour with all the transit commuters going/coming from work.

Post script (subs to post above)

Having reread your post I think the Intercontinental and Park hotel would suit you best. The Intercontinental is very close to theatres, Roy Thompson concert hall and a good number of the better restaurants. The Park hotel is close to Yorkville for upscale shopping and dining.

For sightseeing - try a walk through the St Lawrence market in the morning. Chinatown will probably leave an impression on you as well.