I think you need to be more specific about where in Canada you intend to go.
Travelling betweeen Niagara Falls, Toronto, Montreal and Quebec City, I did use the train and it was fine.
From that region to Calgary/Vancouver, I flew. I flew also from Calgary to Vancouver but I did look at travelling that route by Greyhound.
In British Columbia, I travelled Victoria, Vancouver and Whistler by bus. It was fine. To go further up BC, into the Yukon, NW Territories and onto Alaska, I used an organised tour.
I suggest looking at the article on Canada on wikitravel for info on how to get around:
Also, advice on rail travel there is here:
I think it would help a lot though if you could more info on where you want to go, how long you've got and your budget. Are you prepared to rent a car?