The decay of Sengoku-era characters -- a chart:
Sengoku Jidai
Sengoku Musou
Sengoku Basara
Sengoku Otome
Sengoku Collection
These are all Tokugawa Ieyasu.
Heh... evolution, or devolution? It's hard ot say...
Seriously though, it would be nice sometime if something was a bit more accurate about the costumes... none of those four modern ones look very close at all. So the only "decay" would be from the top, original one to any of the latter four; I don't think there's any decay from those male ones to their recent female counterparts, no.
Can't they agree on whether she should have pink or green hair, though?

You know, like how Ikkitousen and Koihime Musou use the same names for their female versions of Romance of the Three Kingdoms characters. That can't be a coincidence.
Collection is definitely a downgrade from Otome.
It's more moe certainly, and arguably even less historically plausible, though Sengoku Otome's costumes aren't too high on that scale either... but whether it being more moe makes it worse or not is a matter of opinion I think.
The Sengoku Otome one is the more credible fighter for sure, though that image doesn't show her armed or with her weapon she still looks more the part than the last one.
Someday an anime will be made of animegaf, but with everyone represented by a kawaii female stereotype.
I call the shy character.
The biggest upgrade will probably come when the sadhouse Oda Nobuna comes out:
http://i.imgur.com/ahMib.jpg
Figures that Oda would wear a bra. Progressive stuff.
Five costumes, all completely insane historically, and the bra is the one thing you notice? THere's a lot more wrong with all of these designs than just that...
If you want to talk about underwear though, panties are a bigger issue than bras; bras only sometimes show up in these shows, but panties usually do, even though Japan of course didn't have either one until the later 19th to 20th centuries. Of course they had loincloths, worn by men, but women didn't wear that... nor did they have clothing anywhere near as skimpy as those are though, of course. But underwear's just one thing, they do so, so much wrong beyond that. Like, that Sengoku Basara version... :lol, I can't possibly imagine an actual historical Japanese person dressed like that... that costume's every bit as historically ridiculous as any of the female ones. That looks more like a Soul Calibur character than anything out of Japanese history. :lol
Until Akechi Mitsuhide-ko kills her for planning to introduce bras to the mainland, then it's another 400 years of sarashis.
But in Sengoku Otome it was all just a big misunderstanding of sorts (Akechi was jealous of how much attention Nobunaga was giving the MC, not realizing that Nobunaga liked her too...), and Nobunaga doesn't die in that fire, she saves the MC and gets out fine! What, that's not how it happened in the history?
Here's what I think of Medaka Box:
- Shouji Saeki is a shitty by the books director who is the most uninteresting long time staffer at Gainax
- NisiOisin is a sack of shit author who offends my very basic definition of good entertainment.
- The art looks like dogshit.
I don't know about these... for the first, I have no idea what the anime's director's track record is, I'd need a list of titles. For the second, what else has he written? I see the ___gatari stuff mentioned, so I guess that. From what I've seen of them (a good amount of Katana and a few eps of Bakemono), they're okay to good, but are prone to stupid plot points for sure... and as for the third, eh, the art in the manga is okay, though I don't know what the anime looks like, I don't think I've seen any of it.
Let's add another point:
- Follows the standard Shonen Jump Sinking Ship formula of switching into a really boring fighting comic when it started to slip in the rankings.
I agree with this reason the most.