Ant-Man was always going to be a hard film to convince people to see cause "it sounds to ridiculous" and ever since Edgar Wright and Marvel decided to separate after creative differences it has had fans spilt if they should go see it or not but in my opinion there isn't an actual reason why fans shouldn't see this movie, I suspect it's going to be amazing and here are my reasons for thinking this:
1) Cinematic first
For this film they used a technique called macro photography which is essentially filming an object really close up, which then then mixed with CGI and green screen to make a man the size of an Ant-Man which from the concept art looks amazing and I believe is a film first because there hasn't been a film shot like this before.
2) Connecting the Universe
Because Ant-Man focuses on two iterations of the Character we will see some flashbacks to around the 1960s/70s/80s with Michael Douglas's character Hank Pym where he will be working with S.H.I.E.L.D, Agent Peggy Carter and Howard Stark, which connects the universe more together and fills in the time Gap between Captain America: The First avenger and Iron Man.
3) It's Different
Just because it is a comic book movie doesn't mean they are all the same for example [Captain America: The Winter Soldier](tag:254973) is a spy/thriller and Guardians of the Galaxy is a space opera and Ant-Man is a heist film it may feel like a Marvel movie but its not going to be a Iron Man copy.
4) It's the 12th Movie
At this point I have faith that Marvel know what they are doing it is there 12th film and they haven't made a "bad" film yet.
It might just be coincidental but a gag that has been running though a few of the Marvel movies is the use of the number 12, Avengers: 12% of a moment, Guardians:12% of a plan, [The Avengers: Age Of Ultron](tag:293035): I'm 12 minutes older than you, now no one knows why the number 12 is used but it Ant-Man being the 12th film it might of been hinting towards the end of phase 2