Very simple sequel that merely replicates the first film. I bet that's what makes these franchises so appealing to film studios, with a film like National Treasure there's always some new and bigger treasure to be found, so you don't have to work hard to come up with a sequel. Just reuse the same cast, throw a different treasure hunt at them and you're done.
I wasn't a big fan of the first film. It felt like an Indiana Jones/Tomb Raider knock-off wrapped in a Disney jacket, meaning it was too polished, too neat, too PG to be any fun. The sequel doesn't deviate from that at all, so once again it feels like the fun was sucked right out of the film.
Cage is way too restrained, the action scenes are dull, the mystery is somewhat childish and the effects are poor. No deaths, no real bad guys, not an ounce of grit of edginess. It's a good thing they stopped after this second film, but it's one of those franchises that could be revived with a single snap of a finger.