One statement I find almost as irritating as the ubiquitous “well, in the manga…” in anime discussions is the assertion that “_ gets better in the second season!” Now, sometimes this is actually true, but it’s important to understand that the act of making this statement implies a hefty bias.
To give you a better idea of what I mean, I’ve assembled some charts comparing the percentage change in number of myanimelist.net users giving a series a given score for each season. In other words, if series x season 1 had 1000 10/10 votes, and series x season 2 had 900 10/10 votes, it would get a 0.10=10% score for the s1->s2 transition. If you believe that myanimelist is halfway representative of the range of opinions held by anime fans, these charts should speak for themselves.
Between seasons 1 and 2, the largest percentages of votes dropping off are between 3/10 and 6/10, numbers that really boost the rating of the show when removed. The dropoffs for seasons 3 and 4 are less biased, likely because most of the people watching at that point are more dedicated fans. For the record, the four seasons of Natsume Yuujinchou are ranked as such: s1-111, s2-39, s3-36, s4-22. The series’ biggest jump in rankings came after the selective loss of votes between seasons 1 and 2, not after the quality spikes, legit as they were, in seasons 3 and 4.
Strike Witches (less I be accused of genre biasing these results)
Strike Witches’ second season is said by some to be better than the original, and is 700 spots higher on mal, but look at how regular that line is. The second series actually loses a fair amount of 10/10 votes, but gets ground back as they lose a higher percentage of votes for each score lower than 9/10.
Nodame Cantabile is an interesting case because the second season is generally agreed to be a step down from the first, a byproduct of changing directors from Kasai Kenichi to Chiaki Kon. However, the pattern of losing more low votes re-emerges in the transition between the second and third seasons, both of which kept the same director.
Let’s take a simplified case to look at what’s causing this pattern. Take a hypothetical anime with 4 viewers: One, Two, Three, and Four. All four have seen anime Q in some form.
One hates it, episode 6 offended his parents/ethnicity/whatever, he watches 5 episodes, gives it a 1, and vows never to get close to it again. Two thinks it’s, well, a decent way to kill time. He gives it a 6. Three thinks it has definite potential and cool moments, but is irked by a flaw or two. He gives it an 8. Four falls in love at first sight and is inspired. He gives it a 10. The show Q now has a score of approximately 6.25 (~5150 on the mal rankings).
Now let’s say Q2, a sequel to anime Q which happens to be equal in every way, comes out. Of course, One stays away from it. Two happens to be busy with a new season of anime he really likes + university finals, and files it away somewhere on his hard disk to maybe watch someday. Three watches it, and, as it has the same traits as its predecessor, gives it an 8 again. Four watches it and sees it has the same stuff in it that he loved last time, gives it a 10. The show Q2 now has a rating of approximately 9. If Two decides to watch it someday, then the 6 turns that 9 into 8 (~450 on the mal rankings), still much higher than the original.
Sequels can vary in quality. Actually, they do. Every time. But there is a definite general trend for them to score higher by pruning off the original harshest criticisms. This phenomenon manifests in simple word of mouth, as well. Because people who didn’t like season 1 don’t watch season 2, you lose dissenting voices who might be warning you about a show’s flaws, which may be the same or different from those of the first season. So you won’t hear nearly as much bad word of mouth about a sequel, because the people who would offer it have already had their say.
So when you hear tell about how much better than the original a sequel is, it usually pays to take it with a grain of salt and check the record of the person doing the telling.