There isn’t really that much to say about this film. It’s really a rehashing of many of the elements of the first Night at the Museum. They use a lot of the same characters and gags (monkeys slapping Ben Stiller, etc.) with very little attempt to make it better. Rather, this one relies more on quirky dialogue and the characters at the Smithsonian not really understanding their situation. This makes sense because this is their first encounter with becoming real so there would be an adjustment period. So, instead of just having a clever little story, they have to use this confusion for the humour in the movie. Really, it’s the only way they could go because the clever little story was used up in the first one.
That isn’t to say that the new characters aren’t funny. Hank Azaria as Kahmunrah and Bill Hader as General Custer were quite entertaining but Hader essentially played Teddy Roosevelt from the first one. And that’s about where its entertainment ended. The characters of Napoleon, Al Capone and Ivan the Terrible had potential to provide a lot of “Three Stooges” type entertainment and they never really go that going. And, by the end of it, I was actually hoping Amelia Earhart would just disappear. A good sequel takes what made the first movie successful and builds on it. For me, that was the dynamic between Owen Wilson and Steve Coogan. In the first one, their interactions were quite funny. But they all but got rid of it for the second one and that was a mistake.
Finally, I will get to the effects. A movie like this has to rely very heavily on special effects to make everything come alive and look believable. It was done fairly well in the first one (released in 2006) and very poorly in the second. This one came out in 2009 and looks like it was using effects and animatronic technology from before the first one. Even the same characters from the first movie looked worse in the second. Everything is jerky and unrefined.
Ultimately, the film is uninspired and I think everyone just got a bit lazy in making it. There’s some laughs and it’s kind of fun in spots. It's almost worth it just for Hader's antics. But it’s inconsistent in its entertainment and quality. Don’t see it.