It's hard to avoid spoilers, but if you considered this movie's plot, which is woven into A New Hope, you can't deny that it is basically Star Wars Episode 3.5, or even a "Prequal" to A New Hope. Once you finish the end you will know what we're talking about - it's epic and demanding to watch the next movie.
Episode 3 is very emotional, there are a few times that get the juices flowing, but the last 3rd of Rogue One is more influential and emotional than Episode 3.
They say Episode 4 and 5 are stellar, but to me that's more on a directive and ground-breaking scale - Episode 5, Empire Strikes Back, has a lot of plot building, which I think is why it gets high ratings... Rogue One, is almost all plot building, which sets Rogue One apart from most of the other Star Wars main movies. My girlfriend and I, we just started watching the Star Wars movies a few weeks ago, and we got to Rogue One -- she stated, on her own, that of Episodes 1 through 6 so far, this one tells "the most story" than any of them, which I agree with.
Knowing what happens in the other movies is what makes Rogue One so emotional at the end, to know what's at stake, and what is happening, and the line in Episode 6, about many lives were sacrificed, rings true every time I watch Rogue One, it puts new meaning into The Rebellion.