Update: Now you can get the G2000 working with sane drivers. Check my post.

My efforts to get sane and scangearmp2 to work with Canon G2000 on Linux have come to an impasse. If you’re willing to shell out $30, there’s a software called vuescan that works with this scanner. It seems to work pretty well except for the fact that you’re stuck with their software to do the scanning. You cant use a third party software.
Get VueScan from here.