I just checked the Garfield minus Garfield site recently, and noticed that it hasn't been updated in two months. It's possible that the administrator, Dan Walsh eventually got tired of maintaining the same "joke" and airbrushing Garfield out of the picture. That's a shame, since there were still plenty of worthy strips that could be mined for endless potential.
Thankfully, the Square Root of Minus Garfield site still has more variety, which I'm a consistent contributor of. (I'm still waiting for them to post the middle part of my Garfield Manga, which they only showed the first and last parts)
It probably doesn't mean anything, but around the same time that G-G started petering out, we were introduced to the first strip of 3eanuts which has an almost similar concept with a very similar layout to the Garfield parody site. The fact that the Peanuts strips are reduced to three panels doesn't help either.
EDIT - and just after I posted this entry, G-G updated their site the day I mentioned their hiatus. I thought about waiting another day before reporting on their sabbatical, but wanted to report two months to the day they weren't producing new stuff. Shows how prematurely reporting on news can backfire on you.