The problem with this debate is that our memories tend to be selective.
Yes, B/W made some legendary games in the 1990s ... but while their batting average was probably better than most, they did also make Popeye, Radical!, Game Show, and other forgettable titles. Then you look at Congo and Cirqus Voltaire - they didn't get much love back then, but are more appreciated now.
While Stern has produced a few dogs, they also brought us TSPP, LOTR, SM, GB and a few others that have become all-time favs.
I'd say that all manufacturers have their share of hits and duds; the memory just gets a little hazy and it's hard to weigh it all fairly.