I grew up with Roscoe Orman, and I suppose that he will always be my sentimental favorite. I even got to meet him as a kid! But Matt Robinson is consistently very funny and edgy, and is probably objectively my favorite Gordon. He is all about improvisation and would be a completely different character if he were forced to stick to the scripted page... like the time Oscar slammed into his trash can and Gordon simply retorted, "Isolationist!"
Everyone has their favorite era, and that's fine. I personally prefer the first 14 seasons, although I still have some time for seasons 15-20. We all come to it with our own memories, so it's silly to assert your personal nostalgia as some kind of objective truth. It's not like we're sizing up the collective works of Shakespeare here.
Sure, season 1 could be a little repetitive. They also had to produce or at least procure every single segment you see on the show that year! All the subsequent seasons had the luxury of being able to draw from (by the mid 70s) a vast catalog of material.
Looking at the totality of what season 1 produced, basically inventing the format, all the new characters (human and muppet) that were created, and all the memorable segments introduced that remained in circulation for decades, is my preferred approach to evaluating it overall.
I don't remember the "isolationist" remark, I'd like to see that one. I'd like to see as much from the early years (say about the first 5 or 6 years) as I can and I am so happy that so much of it has resurfaced over the years.
Just the other day I saw show #900 via You Tube -- I'd never seen it before and it was an absolute scream! About the first half of the show takes place in Ernie and Bert's bathroom where Bert just wants to be left alone and take a bath. So of course, Ernie wheels the piano in and starts playing some tunes, and then just about everyone in the neighborhood joins in. It was utterly hysterical.
Roscoe Orman was great as Gordon, but of course I'm biased as Matt Robinson was the Gordon I knew. It's really too bad he didn't want to continue, but I understand he wasn't really comfortable in front of the cameras and he more or less agreed to take the role under duress, thinking it would be for a year or two and he could move on. I completely get that.
But in 1972 I knew nothing -- all of a sudden here's this other guy calling himself Gordon, with no real explanation. I never really "got over" that. And although I saw Matt Robinson's name here and there in the credits of this or that show, I never really knew what had happened to him until 28 years later when I got on the internet and he was towards the end of his life. I would like to have met him. I had an opportunity to meet Roscoe Orman once when he appeared at a mall, but I was working at the time and the lines were huge, so I didn't actually meet him.
I think my favorite "Gordon moment" is the business with Oscar's "wet paint" sign on his trash can in a Season 2 show.