I came on board with Wing Commander not too long before Wing Commander 4 came out; I had the game in my hand about 2 months after it came out (since I was broke and in high school), so when I think of WC, I tend to think of a blending between III and IV.
Paulson was integral to my WC experience. In fact, the person who introduced me to the series would refer to teachers we didn't like as "Paulson" (a name we said, dripping with overly-dramatic false disdain) and another teacher we enjoyed having as "Tolwyn".
I got the feeling John Spencer was kind of pigeon-holed into the role; he played it effortlessly, sometimes bordering on complete characature even when WCIV wasn't the most subtle of stories. But the more I saw of his short role, the more I realized that he was *really* good at it. The reason he was casted (type-casted?) into the role was because he was just that good at playing a jerk and brought more to that role than a lot of bigger, bankable stars could've.
I'm sorry to see him pass on. He was one of those faces that popped up on my TV from time to time and I enjoyed giggling to myself when no one else would ge the joke. I hope he's at peace.