The Muppets, as a franchise, seem to suffer from a huge "rubber band" effect when it comes to expectation for their output. Both their TV shows and movies run through cycles of anticipation, enjoyment, wildly varying quality, and even general direction, ranging to rag-tag caper films, historical adaptations, and god knows what else, rising and falling in popularity as it goes. I'm of that generation that grew up with them on the TV and in my Record Player, so they're somewhat ingrained on my conciousness, but they've managed to transcend generations, which is no mean feat. And then a couple of years back they made The Muppets, which was rooted in a deep love for what they represented, and managed to be about more than just it's "getting the band back together narrative" and be something really touching. Inevitably, as they sing in the opening number, there is a sequel.
Muppets Most Wanted gets its defense in early with that opening number, claiming that it's never as good as the original, and they don't really know what they're doing. It also lowers my personal expectation by having Ricky Gervais in it, who somehow manages to grate on me in whatever he's in, but as he's supposed to here its actually not much of a problem. It also manages to have its cake and eat it by landshading how lazy the "world tour" setup is, and later how silly the "evil twin" story is, but this is the Muppets, man, and that's just how they roll.
In fact this is a very traditional Muppet Movie, and only serves to highlight that The Muppets was a little bit of an aberration. The gang move from set-piece to set-piece, getting into a thinly connected series of scrapes and meeting a lot of blink and you'll miss it cameos from actors who, you often get the impression, just wanted to be in something with the Muppets. There isn't a lot of character development, clever plotting or depth, but there are a lot of jokes, some good, some so-bad-they're-good and some that are just bad, but they're think and fast and there is always another one along in a moment.
Holding up the human end of the movie is the aforementioned Gervais, and despite my general reservations is well pitched and a good foil for the Evil Constantine. More wasted is Tiny Fey, who gives it everything, and is such an inherently funny performer its hard not to like her (yes, I have crush after 7 seasons of 30 Rock. Who doesn't?) but I was waiting for a bigger gag to come from the character and it never did. Rounding it off is Ty "That Bloke from Modern Family" Burrell, who gets to deadpan it up with Sam the American Eagle in a partnership I could totally stand to see more of.
I have to agree with the broad consensus that Muppets Most Wanted isn't as good as The Muppets. For a start its not as unexpected, its not as warm, and it doesn't have the clean emotional lines of it's predecessor. But actually it is a pretty good film in it's own right. It's funny, the songs are good, the performances are engaging. It bounces along with confidence and joy, and has that great Muppetty sense that this is all a game, and we're all in on the joke. And thats what it's all about, right?