Detroit wins. If that is what you are asking, the answer is: Detroit wins this trade.
Seattle is cleaning house. It is attempting to reshape an inherited roster around a new philosophy and a new scheme, and it is accepting losses in the process. It could not hope to trade a former 28th overall pick for a comparable pick in the 2011 draft, and it hasn't. We do not know what the Lions have traded in exchange for Jackson, but it is not a late first round pick.
Unlike San Francisco trading Kentwan Balmer, Seattle is not cleaning up an unfixable mess. Jackson was not holding out. He was not bench bound. Seattle could have started Darryl Tapp at right defensive end and Jackson at left defensive end. That wouldn't be a great line. It would probably be pretty lousy. But it would be cheap and young and capable of growth. It could be supplemented over time. It could surprise.
Jackson was not a bust, either. His production over his first two seasons was comparable to many ends that eventually broke out. A quick survey shows that Jackson ranks fifth in career sacks among defensive ends from the 2008 class. He is behind Trevor Scott, Cliff Avril, Chris Long and Calais Campbell.
Some will be satisfied to say Jackson sucks and be over with it. Some will be satisfied to say Seattle has traded away talent and be over with it. There isn't a simple answer that encompasses the trade. There is a series of events that started with Jackson's rookie season and came to a head this spring.
Jackson had his problems. He quit on plays as a rookie. He started 2009 strong and then disappeared. Like Balmer, Jackson is too young to write off but significantly less valuable now than when he was drafted. Jackson is young and cheap and there was no urgency to move him. He could have been a significantly better player this year than last. Next year than this. Worth franchising by the end of his rookie contract. Who knows exactly how young players break out, but they do. This time last year, who the heck was Sidney Rice?
Detroit wins this trade because the Lions have bought low on a still very good, very young and very volatile talent. Detroit wins because Jackson still has much better potential than a mid- to late-round draft pick. Detroit wins because Seattle had schemed Jackson out of its defense and had to either sell low or burn a roster spot on a misfit.
That Detroit wins does not mean Seattle loses. It lost, insomuch that it did lose, through the process of taking a good talent and depriving him of a position and a future. It mitigated that loss, perhaps fully, by salvaging another good talent by giving him a position and a future: Red Bryant. And though Jackson was selected in the first and Bryant in the fourth, there is not a ton that separates their intrinsic "talent." One might argue that if Bryant was not transferred to end then he probably doesn't make the roster. And so Seattle could not have retained both Jackson and Bryant.
And that closes the loop: Seattle drafted Jackson but Jackson never busted nor excelled; Seattle drafted Bryant but Bryant proved incapable of playing tackle; Seattle found a home for Bryant by scheming Jackson out of a position; and, that done, Jackson no longer had a place on the roster. Jackson had become a loose end. Now he is gone.