DANNY COLLINS
Although a side plot gets in the way that schmaltzes it up a bit (the whole thing could trim by 12-15 mins anyway), the initial premise is way way cool and is based on a real event: A musician learns, 34 years later, that John Lennon sent him a personal letter. This fact brings him to re-evaluate his life and he wonders what life woulda been like had he received the letter in 1971, esp since the letter contained Lennon's personal phone number.
The movie totally fictionalizes a plot after that but it's still decent to watch. And the cast: Al Pacino, Bobby Cannavale, Annette Benning, Christopher Plummer, Jennifer Garner.