I am a fan of the Marvel Cinematic Universe films and a super fan of the WB/DC Justice League Universe films, so I will be thrilled if Captain America: Civil War goes on to have a huge opening weekend, just as I was overjoyed to see that Batman v Superman: Dawn of Justice pulled in the largest March opening ever and the 4th largest worldwide opening of any kind.
But as the general consensus forms around Civil War, this is a good time to contemplate the limitations of the various metrics that are used to calculate critical reception. An unfortunate feature of today's movie culture is that the Rotten Tomatoes "freshness" score has come to be the most prominent indicator of a movie's critical reception. This is unfortunate because the RT "freshness" score is probably the worst amalgamation metric, operating in a completely binary fashion (registered critics enter a review and a numerical rating but the freshness score is only calculated based on whether they pick fresh or rotten... that's it).
As I explained when Batman v Superman first came out, the story about those reviews should have been about the fact that they were mixed or polarized, with many people rating the movie positively, a lot rating it right around 5 or 6 out of 10, and then another chunk rating it below average. The problem with the RT freshness score is that if a movie has lots of 5's or 6's out of 10, those all count as rotten. A movie with 100% ratings of 5/10 would have the same freshness score as a movie with 100% ratings of 1/10.
Batman v Superman had a lot of reviews around the 5/10 mark and so, even though its average rating was around 5.1/10 on its opening weekend, its freshness score headed toward 28%. The average was a better measure, as confirmed by the MetaCritic rating of 44/100, which is considered a moderate-category rating (MetaCritic regularly has movies come in below 40). But unfortunately, much of the media and social media narrative latched onto the freshness score and it became functionally true that BvS was hated by critics because it was repeated and cited so many times.
What does this have to do with Civil War? Well, currently the new MCU film has a Rotten Tomatoes freshness rating of 92%. So wow, it must be one of the best movies of the year, right? But actually, the average rating on RT is 7.5/10. Now, that's still a solid rating, and it's definitely a better critical consensus than Batman v Superman (even though I personally think BvS is a masterpiece, if not a crowd pleaser), but my point is that a 7.5 isn't exactly blowing people's minds. Corroborating things over at MetaCritic, Civil War currently sits at 75/100. Positive, but not crazy good. It's just able to take advantage of the freshness score limitations, where a lot of 7's out of 10 translate into all fresh rather than rotten (the same as if it were all 10/10's).
The sad thing will be if the media and social media narrative becomes fixated on the misleading 92% number rather than the more meaningful 7.5 number. Of course, this is not sad for Civil War but it's just sad for BvS because the latter was unfairly tied to the misleading 28% number, and the two will seem to be widely apart in critical reception when really it's a situation of BvS being reviewed as moderate quality (with divisiveness) and Civil War being reviewed as slightly above average (lots of consensus around 7/10 or 8/10).
EDIT 5/6/2016: Here's an academic look at what's going on between film critics and the anti-Snyder, pro-Snyder fans.