I just looked, and GotG is 10/20, so truly right in the middle (for now).It is funny when folks say 'old Marvel movies', it is easy to forget that none of them are more than 10 years old. They've just produced so many that it seems like we have decades worth.
In case anyone is curious about the franchises and where they fall in the placement of things, you’re welcome:
Iron Man- 1/3/7
Captain America- 5/9/13