The Simpsons are one of the most well-known (animated) TV families, sporting a cultural impact that went far beyond their own fandom. They remained faithful to the TV format for the longest time, but considering their immense popularity, a film adaptation was always going to be inevitable. In 2007, almost 20 years after their inception, it was finally time to make the leap to the big screen. And while the film didn't ruffle too many feathers, it was a worthy adaptation that did justice to its franchise. Even revisiting it now, it's still a small bundle of joy.
Eventually, I lost interest in the series. It wasn't so much because I felt the quality had declined, it's just that the series inevitably started to feel repetitive, and I had less time and energy to spend on TV series in general. It's difficult to understate the impact it had on me growing up though, as I think a lot of my comedic sensibilities were developed by watching The Simpsons. Its biggest appeal for me was the rather wide variety of comedy the show had on offer. From simple puns to running jokes, parodies, caricatures, and pure absurdity, it offered a perfect amalgam of laughs for a teen discovering the varied stretches of comedy.
Like any film adapted from a TV series, there's no escaping the fact that it feels like an elongated episode. For a film like this to become truly cinematic, it would have had to deviate too much from its original format, which would then have alienated too big of a portion of its fans. And a film like this is made because it comes with an enormous fanbase built in (read an almost certified return on investment). That said, they did a proper job fleshing out a single-episode narrative to feature length, with enough room to pay homage to the series and to have a little fun with the cinema format.
Springfield is dealing with an environmental crisis. Its lake is one spill away from going irreversibly toxic, so rigorous measures are taken to keep people from dumping their garbage in the lake. When Homer takes in a pig he has to get rid of its waste, he ignores all the warnings and dumps them in the lake. The EPA has to act and decide to put a big dome on top of Springfield in order to protect the rest of the US from their irreparable antics. When word breaks out that Homer is the culprit a mob storms The Simpsons' house. They manage to escape through a sinkhole and the family turns its back on Springfield.
The film had a considerable budget, which is reflected in the quality of the animation. There's more attention to detail, the animation is more fluid and some of the scenes had technical challenges they wouldn't have been able to pull off in a TV series. There were limits to how far they could take it though. The Simpsons has a very recognizable art style, which is in part linked to its visual simplicity. You can't just get rid of that, only because you have a bunch more cash to burn through. I think they handled it pretty well, the only downside is that after a while you don't really notice the difference anymore and it starts to feel as if you're back to watching a regular TV episode.
The voice acting is on point, but that's no real surprise. The main cast was present to reprise their roles, so everyone sounds exactly the way he should. The voice acting has always been a strong point of The Simpsons, with characters sounding very distinctive (even though some are voiced by the same person), but never too grating or caricatural. That's the upside of using professional voice actors over celebs' names with poster value. Safe to say, it's best to stick with the original dub, unless you've gotten so used to watching the series dubbed in a different language (though this would be the ideal opportunity to finally make the switch). The soundtrack is considerably less interesting. It's just background noise with very little function beyond that, but for a core comedy, that's not too bad of an offense.
Even though the franchise was always very focused on comedy, many of the series' episodes had quite ambitious plots. With only 20 minutes per episode, they always felt rushed and unfocused, with too much crammed into too short of a time span. A feature-length film gave the team more wiggle room, and they used it appropriately. It's all still just a bit of nonsense that serves as a single big hook to work in as many jokes as possible, so don't expect anything too eye-opening. There are just fewer sudden jumps and weird leaps of logic to come to a proper conclusion.
The Simpsons Movie fits the brief. It's a film that doesn't deviate too much from the original show but adds a bit of extra appeal that wouldn't have been possible if it had remained stuck on TV. The film won't win its franchise any new fans, yet fans of the series don't have to worry the film may taint The Simpsons' reputation (or what is left of it anyway). Personally, I found it a fun way to reconnect with the show, then again I don't really see any option to revisit the TV series, so your mileage may vary. One of the better small-to-big-screen adaptations I've seen.