I think the general movie was great, although I thought the whole "entrap springfield in a dome" storyline was a little far fetched even if it is in the simpsons universe, as it seemed a little too Dr Evil mastermind style plot to me (you know the zany crazed general / evil mastermind angle) and the story was too Homer centric as we have enough Homer stories in the series.
Personally I think a sideshow bob story or a minor character story would have been better.
I didn't even wanna go see this movie (my brother dragged me to it) as I feel the Simpsons has been on the decline for at least the past few seasons. In the end I found the movie to to be like an average episode, funny parts, but not the greatest. I feel like this was more of a last ditch effort to make some more $ before putting an end to the show. 3/5
Oh and Futurama > Family Guy > "new" Simpsons (old ones come 2nd)