It's just not the kind of question I'd find myself asking. I don't buy enough games to have to limit myself to "just 5" of one designer, unless you count expansions. Which I guess loops back to my earlier statement that new games are like expansions to Euro fans. I couldn't even think of five games from Rosenberg off the top of my head until I read the thread.
I mean, I like Richard Garfield. I like Magic, King of Tokyo, and Roborally. But I'm not gonna run out and get Ghooost even if I did think it was pretty neat. I don't have KoT yet either, but I think I will eventually because my nephew loves it.
The funny part about the Rosenberg thread was that she set the limit at five. You can just hear the gears turning in her head as she wrote it, probably starting with three, realizing that she didn't want to leave any of her favorites out of the list, ok, FOUR. No! Five! Five favorites! It would have been six if there had been another Rosenberg title she liked.