If you are a comic fan like myself then you've already watched the first two movies...The Avengers and Avengers: Age of Ultron. For the true purists you have undoubtedly watched the Iron Man trilogy, The Hulk, Thor and Captain America as well. Marvel is cranking them out at a phenomenal pace and I love it. Oh they have released other blockbusters outside the Avengers genre i.e. Spider-Man, X-Men, Daredevil (now on Netflix) and recently Deadpool.
Lets not forget about Marvels counterpart DC Comics. They have a long running history of Superman and Batman movies. Over the last decade they have rebooted the series with 'Superman: Man of Steel' and 'The Dark Knight'. The new Ant-Man movie looks promising too. They have taken a more direct route by featuring a handful of heroes on the CW network featuring Arrow, Flash and currently DC Legends of Tomorrow. It's no secret a 'Justice League' movie is in the works. Closest thing to that right now is Batman vs Superman: Dawn of Justice coming out next month which seems to feature a slew of DC heroes mentioned above.