So in my opinion there are only FIVE movies is the MCU. Those movies are Iron Man, Incrediable Hulk, Thor, Captain America: The First Avenger, and Gaurdians of the Galaxy. So now I bet you are asking yourself why these five films. My logic is that they are all the first films of their respective franchises. They carry none of the baggage that sequels do, and none of the weight of a post Avengers MCU. So below I am going to give you my list of how i personaly rank the origin stories in my MCU (from worst to best) and then say why I think Ant Man fell where is did. Really won't talk about the other films because admit it its been done to death.
4. Ant Man
3. Captain America
2. Guardians of the Galaxy
1. Iron Man
So now why did Ant Man rank fourth? The movie is not bad. I have read many posts saying it is the worst thing Marvel has put out and others that said it is the best. the truth according to me is that it falles squarely in the middle. The movie was grounded. it centered on a regular working class guy with a daughter and no power what so ever when he takes off the suit. Ant Man was also EXACTLY what it was billed as a HEIST film. Yes there had to be the scene to tie it into the greater MCU(which is why i personal think Edgar Wright walked). That being said I think that Payton Reed, Paul Rudd, and Adam McKay did it with out comprimining the story. And then the third act is probably the best one Marvel has ever done. It took the mundane items of a childs room and turned them into a throwdown for the ages. So to wrap this up, Ant Man had heart, humor, mind blowing VFX and no baggage and that is why i ranked it fourth.