I had a felony for domestic violence, didn't have money to fight it then. I have traveled through Europe and Mexico and Central America since and never had any problem.
Would Canada be a problem?
Well, there is always the possibility. But taking into account the fact this felony was from 15 years ago, I think you should be fine. If your record has been clean ever since and that felony is your one and only on your criminal record I would say you will be fine.
However, if your criminal record has multiple felonies and offences and anyone of them were recent, you could definitely have a problem on your hands. It is worth speaking with an immigration lawyer, but probably not required. Calling the consulate might be able to help you as well (they generally suck at giving advice over the phone though).