The thing people nowadays don't get about Classics like this one is the fact that they last forever.
If you are used to watch movies from the 20th century (in general) they are flat and have no depth, there is no doubt that you'll enjoy them but that's that, you will forget them the minutes they're over.
And that's what makes this movie beautiful, aside from the beautiful performances and beautiful story, there's a great moral behind it, it gives you new meanings every time you think about it.
James Stewart is an awesome actor, the fact that he played a character that was supposed to be 27 years old while he was actually 10 years older really shows his performance.
And there isn't much to say about this movie other than the fact that it was beautiful and had a great moral behind it, That your life matters even if you don't feel that way, but you are connected to so many people and have so much influence on the environment around you that people around you won't be the same if you weren't there.