The Dictator has it's moments but most them you will have caught in the preview. The idea, like other Cohen works, stems from grandiose satire played out through odious comedy and faux documentary stylization.
Ali G has come a long way since his HBO TV inception but maybe not in the right direction. I have not much cared for any of his film acting gigs in Hugo or Sweeny Todd and his four other starring vehicles are usually are found wanting. I did find Borat, however, to be the best of the four and really it was quite well done. Larry Charles has directed three of Sacha's efforts and the comedy of result is, I would gesture, 65% effective or thereabouts. You have more hits than misses but still too few direct hits. That being said, I enjoy Cohen and I hope he continues, he is like a comedic version of Michael Moore and continually rubs peoples noses in their own stank - not for his purpose (hopefully) but for genuine exposure of the truth as he and many others see it.
The only redeeming quality of The Dictator was during the few ending statements when Cohen monologues what a great country America would be if under a dictatorship, in which he ironically summarizes all the laws and atrocities that are contemporaneously occurring under our present 'democracy'. It's preachy, yes, but better than Bobcat Goldthwait's recent attempt with God Bless America and as good as something you might see on the Daily Show. Satire is and will be a great way for memes to stick and pass on important ideas for future generations.
Recommended Viewing: Borat - General Idi Amin Dada - Waiting For Guffman
Bob Scale: Objective: 6.0 - Subjective: 6.5
Rotten Tomatoes: 61