I know Gamasutra (www.gamasutra.com) has a pretty big listing of game companies and their locations, you could try looking there. There's quite a few top notch game companies there, Bioware, Digital Extreme, Ubi Soft, etc.

Here's two more for you...
Sir-Tech in Ottawa -> http://www.sir-tech.com/
Strategy First in Montreal http://www.strategyfirst.com/

How can you forget about Relic Entertainment? The makers of the ever-so-addictive Homeworld. They're based in Vancouver BC.
web site at: www.relic.com (I think)

Or Electronic Arts AKA EA, based in Surrey, BC!

Hi
I need a list of web-sites or just names of all Game Development companies in Cananda , Can anybody help ?
Thanx

BioWare Corp, the guys who developed Baldur's Gate are based in Edmonton, Alta.