If you just go by the numbers, probably not. G1X sensor is not THAT much bigger, whereas the 20mm lens is quite a bit (1.5 stops) faster, plus is a prime with many fewer layers of glass muddying things up.
That said, with the Canon you do get a nice 4:1 zoom into the bargain, and Canon JPEG quality, which I've long put right up there with Olympus (and way above Panasonic's artless attempts). I keep coming across old snaps from my Canon 1/2.5" superzoom whose overall aesthetic in terms of color quality equals or exceeds anything I've gotten out of my G3. AND it had a usable Fill Flash function! Obviously I can't print the 5 MP JPEGs at poster size or rescue blown highlights in Lightroom, but within their limits they're really nice to look at and do exactly what I wanted them to do as photographs.
I"ll probably hold onto the G3 since I'm not a camera-a-year kind of guy, but I will be pretty curious to see what sort of images the G1X can make.