A hypothetical viewer going into The Bourne Legacy who hadn't seen any of the previous Bournes, and had no idea who Jason Bourne is, would be confused to the point of irritation by this movie.
That's not meant as a criticism, exactly, but an observation. Legacy assumes from the get-go that you're at least kind of familiar with the Bourne franchise, and I suspect one would get more out of it if one had a better memory for the details of the previous films than I do.
Which brings me to an actual criticism. When I heard about Orson Scott Card's Ender's Shadow, I elected not to read it, and I thought of that book while watching Bourne Legacy. I have a problem with the whole concept of a narrative taking place in the background of, and therefore having no impact on, the main narrative that we're already familiar with from the preceding big hit. For die-hards, I imagine it's not much of an issue—i.e., if Peter Jackson made a The Librarian of Minas Tirith spin-off movie (or, more likely, trilogy), I'd be excited even while complaining that it strikes me as a cheap cash-in.
That said, Legacy is an effective cash-in. Legacy is highly watchable from start to finish, well-paced and well-acted across the board. Jeremy Renner plays our ambiguously-named hero, and his character is much less dour than Jason Bourne, which was refreshing. Rachel Weisz portrays just the right balance of competence and panic in her role as the civilian thrust into a desperate escape. The main villain is the always-welcome Edward Norton, bringing subtle humanity and complexity to a part that can easily become comic-book simplistic.
Action fans shouldn't miss The Bourne Legacy, but fans of stories that defend their own right to exist might have mixed feelings. When you get right down to it, there's no reason why this movie had to have anything at all to do with Jason Bourne, except branding. That realization led to a sense of distaste as the credits rolled, not quite strong enough to overshadow the enjoyment I'd experienced, but enough to color it. And I really don't know what the hell to expect from The Bourne Inevitability, The Bourne Nonsequitur, or The Bourne Interminability. I'd be unsurprised, but disappointed, to learn that every sequel is going to have a new lead, going through the exact same general story beats. (Sort of like Bond, in fact.)
Still…I suppose that's preferable to franchise-reboot after franchise-reboot.
Star Score: 3.5 out of 5