Fantastic Four, especially #232-256, as well as his earlier #220-221, and the pencilled issues before those. It's 'don't get me wrong' about #257-294...there's still some outstanding stories in that heap of issues (particularly IMO, FF #'s 262, 267, 271-273, 276-277, and 285), but that half of the legendary FF run was unfortunately rather inconsistent and rushed in places due to Byrne also working on
Alpha Flight and
The Thing at the time. The older I've gotten, the more I feel and think that you simply cannot beat FF #232-256 for the sheer consistency of its writing and art...something that has always been rare, and especially a lot more-so now.
BTW, I say it A LOT, but if I was pushed to name my utmost favorite FF issue ever, it would have to be FF #236. I heart "Terror In A Tiny Town" to the point of grabbing some actual FF #236 color guides by Glynis Wein when I saw them available last year. To this day and forever, it is an absolute honor to own pieces of the process of one of the finest, purest FF tales ever conceived AND grandest creative runs ever.