Those were a great set of issues, and the run stayed strong up to about 33 or so, too. 42-50 were a good read as well. I recently completed my run from 1-78 and once I get all my stuff unpacked from a recent move, I'm going to read them all, one per night.
I love GI Joe. I still watch the cartoons on DVD. In the comic's heyday, there was no title that made you anticipate the next issue more. Even the kids in my neighborhood who didn't read comics in general, looked forward to the next issue of GI Joe. Who didn't camp out at the comic store for the origin of Snake-Eyes?
The stories were great about Zartan and how he killed the hard master. It got a bit silly when they made Serpentor though. They started to cave to Hasbros demands and just made crappy issues from there on out. It was a shame.