JVC DV-GR800 and Canon GL2
 

which one is better in terms of resolution ? for sure overall, Canon is better , but I just trying to figure the resolution thing, still don't understand, some people say, Canon GL2 has effective resolution of 0.68MP, then JVC 800 probably has greater resolution, ( not color correction ), so is this true ?

The inital pixel count would dictate the final resolution, if the image wasn't then getting scaled down to 720X480. The perceived resolution is coming from a mix of the initial pixel count, the lens' glass quality, and the quality of the image processor.
If the JVC has a crappy processor and/or lens the higher pixel count won't matter. It is most likely that the GL2 has better glass, and probably a better processor as well, as it has to be able to handle 3 simultaneous signals.
Although the images aren't geting scaled down, the same concepts apply to Digital Still cams, which is why reviewers are reminding people not to just go by pixel count anymore.