Best TV cartoon turned film

[The Lion King]

I like all of them (even the South Park movie had its moments), but am going to have to give it to The Simpsons Movie. Being one of the biggest long time fans, watching it in the movie theatres was like a whole new experience for me.

The Simpsons Movie - A+ - is very epic and funny. Nothing like this has been seen from The Simpsons since the classic era
Stewie Griffin - The Untold Story - A+ - absolutely fantastic. Marks exactly where Family Guy was at the top of its game. Has perfect animation, sharp satire and is one of the funniest movies I've ever seen
South Park: Bigger, Longer, Uncut - A- - a lot of things in the film just confirm why the show annoys me, but even I know that it was a really huge step up from the series at the time and has some really good scenes
Bender's Big Score - N/A
Aqua Teen Hunger Force Colon Film For Theaters - N/A