I was going to make a thread for this idea but was fairly sure I wasn't the first to have this idea so I checked and lo and behold.
Well this thread is about trailers and the movie itself doesn't have to be good. I present what is to my mind an excellently done trailer: Teenage Mutant Ninja Turtles 2: Out of the Shadows.
What makes this an excellent trailer? Well, it teases every element that fans want with just enough of it to make you hungry but manages to not give away all the cool stuff of the plot:
A glimpse of Rocksteady and Bebop before and after transformation, you see parts of what fans will work out is the Technodrome which means Krang but you don't see Krang so you want to see the movie to see what Krang is like. You got about a six second supercut of Casey Jones (man, Stephen Amell deserves bigger roles). Baxter Stockman being dorky. It's all teasers that grab your attention and light up those synapses.
Now the pacing of it. Yes, you have the skybeam bwaaaah opening but they use that lull to set up the It's Tricky beats and it's really a perfect song for trailers - anticipatory opening going into a fast thumping base to set the action to.
The action? You have a tank coming out of a waterfall firing a shell at a turtle on a tyre pulled out of the way by the turtle's brother whilst a rhino punches the air, van fights, Megan Fox's midriff for the teenage boy market. Whole thing is a tight < 3mins.
Second up, There Will Be Blood. This trailer makes the excellent decision to open with part of Danial Day-Lewis's monologue. He's a great actor and the monologue is a sales pitch he makes so there's an element of subtle distrust about it and the strings come in a half-beat after his first line adding a very classic and sinister undertone to the whole trailer. It's filled with long wide shots conveying the epic feel of the story and close in shots of actor's faces. The trailer makers had a lot to work with because the writing in this film is exceptional. Day-Lewis's "I want no-one else to succeed" gives the audience chills. And there are lots of little unsettling moments like the faith healing which paints a picture of a society with fewer rules. The whole trailer is a constant back and forth between tight little character moments and then epic events, fires, rigging collapses, back and forth, back and forth. Ending with those sinister strings. Very good trailer.