This is worse than just "some down time", when you consider they haven't been to the playoffs since the 1999 season...and they don't appear to be going back anytime soon. The only team that comes close to Detroit that I can think of is Houston (unfortunately)...they've been around since '02 and have never been to the playoffs, and like the Lions, don't appear to be going any time soon. The Cardinals haven't been since 1998, but I'm assuming they'll go this year.
Just to add to the pain of Lion fans, I'll throw this one out as well...Detroit hasn't won a playoff game since 1991. Almost 20 years!
EDIT: I guess I overlooked San Fran...they've been pretty bad for a while now, too. I think their last appearance in the playoffs was the 1998 season.