This is the first thing that came to mind for me as well. Have always loved how mean everyone seems without the canned laughter to tell us "hey, this is funny!"
You won't find me defending The Big Bang Theory, but it's worth noting a lot of actually funny television would have this kind of dead energy if you removed the laugh track, because it's both written for that environment and paced and acted for the audience reaction breaks.
True, the awkward long pauses between each beat are there specifically for the laugh track and if they had gone without the track they wouldn't include the pauses either.
I don't think this came about by randomly deciding to take a character out of a strip. The creators of G-G recognized that Jon is a depressing character who has these one way discussions with Garfield. Garfield's inner monologue (that Jon is not aware of) provides all the humor, mostly at Jon's expense. Take the humor out of the comic, and you're left with the depression. It goes straight from a comedy to a tragedy.
This is what's interesting about G-G. The tragedy was always there. We kinda knew the tragedy was always there, but we'd rather laugh at Jon with Garfield than commiserate with Jon.
Taking superheroes out of a random movie would lead to silliness, yes, but nothing poignant.
or took soem movies and made all the villains super-attractive and the heroes ugly and dressed in black.