I've been thinking about popular shounen anime series. By that I'm talking about series like Naruto, One Piece, Bleach, Dragonball Z. Any long-running butt-kickers where the heroes go from fight to fight.
Now, I have no problem admitting that I like watching them. They are fun, they don't require a massive knowledge of Japanese culture, you don't need to think. They get a lot of snobbery from the otaku community but in the end they get the job done without any pretensions.
However, they all commit the exact same error. See, in them the ability to win a battle is the only important thing, and the only way to win a battle is through strength. This means that if the writer wants to create tension he has to introduce an enemy who is stronger than the main characters. Since the only way to win battles in these series is by strength, that means that basically the heroes have to train until they win. Then, when the story continues, a new enemy is introduced and they have to be even stronger, requiring further training. DBZ was the most honest about this phenomenon, even introducing a numerical power level to let you know who was going to win. Goku starts off the series at power level 400 or so. Within a couple of volumes he is at power level 9000+. So the only thing the creator can do is introduce Frieza, with his base power level of 530,000. Let's continue DBZ as an example.
1. An enemy who is stronger than Goku arrives (Raditz). Goku and Piccolo team up and defeat him. Not too bad so far. However, Raditz warns them of the impending arrival of an even more powerful enemy, Vegeta.
2. They train. They beat Vegeta.
3. An even stronger enemy appears in the form of Frieza.
4. They train, they beat Frieza.
5. An even stronger enemy arrives in the form of those androids.
6. They train, they beat those androids.
There is no sense that battles can be won any other way. This produces some really wierd things. Frieza was supposed to be the most powerful being in the universe, yet by the end of the series dozens more people who are stronger than him have appeared.
Look at the same phenomenon in Naruto. The first major villain is a renegade ninja from the water country named Zabuza. Now, he is a jonin-level (high) ninja and, with his strong sidekick Haku, is a force to be reckoned with. So what do Naruto and his companions do after their first confrontation? They train. They fight again and eventually win.
Then in the next arc their enemies are genin-level (low) ninja, such as Gaara of the Sand and Hyuga Neji, and still they are more of a problem. So what happens? They train, they defeat them.
Now in fairness to Naruto there is at least one character who wins his battles on intelligence, which is what I would like to see more of. What I would really like is one of these long-running shows to have a hero who stayed at about the same level all the way through, and instead win their battles by outwitting their opponents. What this would mean is the opponents needn't necessarily be significantly stronger each time. It would also be more interesting to watch, and it would feel like the hero had earned their victories, instead of having them handed to them because their power level was higher than their opponents.
EDIT: I just realised the other reason why this bugs me. The main character tends to gain a lot of power much more quickly than anyone else. Look again at DBZ, where first Yamcha became irrelavent, then Tenshinhan, and then even Kulilin (my favourite character, btw) to an extent. In Naruto it's the same. There are twelve genins who could be said to be 'sidekicks', roughly equivalent to the Z senshi from DBZ, yet at this stage only Naruto, Sakura, Neji and Shikamaru actually DO anything. It's been far too long since we saw what Shino, or Hinata, or Tenten, or Ino could do! When you start to like certain characters, and then find that they basically get written out, it really gets annoying.