I can't think of an episode I hate in the way people say they hate episodes in the posts above. There are a few I might only watch once or twice (some episodes I just watch over and over), and where the storyline doesn't particularly grab me, but none that I hate or think of as 'worst ever'. I didn't like 'Fare Game' because people were eating FRIED SPIDERS and I HATE spiders, but then I disliked the first episode of CSI Vegas s10 for the same reason, I really could have done without the close ups of the spider. Or any mention of spiders. But I like the storyline for Fare Game, it's just the spider bit I can't stand.
I agree GFD was improbable even to the point of being ridiculous at times, but I just enjoyed it. Unlikely? Yes. But hey, this is the Land of CSI, where Horatio can kill heavily armed drug gangs with his sidearm, or Delko can get shot in the head and be back on the job a month later. Things like this I see as amusing quirks of the show rather than a bad thing, but I can understand why it would annoy people. I think it's a real shame they didn't get to really go to Greece, though.