I would say that it has all pretty much stayed the same. The problem is that we've read the older manga before, so now the cliches that they all used are in every other manga out there (if it ain't broke, don't fix it). A lot of the 70's and 80's art wasn't great...a lot of it looked the same, but they had the story behind it to make a great manga. Now, there is so much on the market, you can find great art everywhere, but the story is hit or miss.

Like someone said before, scan teams seem to be everywhere now, so we are getting all manga that are being released instead of just the gems from previous decades. This may make manga standards look lower, but it is still nice to see that new mangaka getting a chance and coming up with something original that would be overshadowed by more epic manga.

Also, I know that they are not actually manga, but there are a lot of webcomics that are looking very promising (weekly stories with around 50 chapters so far). It helps that they are all from a different cultural perspective, though. There are still cliches, but they are tweaked a little bit.

great korean manhwa with good stories and art keeps coming out while japanese still favor manga with 6 yo wearing school swimsuit...

I don't think much has changed.

I do think the art of manga these days has improved a lot.
Plot wise though? Meh.

With the volume of manga that comes out, scanned or no, there are bound to be stinkers. I say just read what you like and don't worry about what you dislike.

This would be easier to apply to anime; anime seems to get stuck in genre and style ruts for several release seasons.

hmm...what are we judging in "quality"? Plot? Art? Character development? A combination of everything?
I don't think it's that easy to tell because unless a series is ongoing, you have no idea about how recently it was published (and with series like Bleach which have been in print for ages it makes it even more confusing!). Even this fails when series like Glass Mask come off hiatus, although with that example you can tell with the art.
Personally I don't think the qualities really changed; I read series that I like irrespective of the year the manga was published.

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I am the master of my fate;
I am the captin of my soul.
William Ernest Henely

I rate manga with 5 being the average score.

Well, I can just agree with some of the previous comments.

Is not that mangas are "worse" today, is just that there is A LOT more of production today. Also, as some people pointed out, scanlations brings us tons of manga that we would be unable to read otherwise.

So to boil it down to a single sentence: there is no less quality, but more quantity, and hence the quality gets diluted.

In my opinion, at some point in the last decades the manga publishing became a huge money making machine. Then, everybody and its mother tried to make money with it. And the market got flooded.

Now sum up an aggressive competitive market and the typical conservative japanese mindset: voila, you got the last generation of mangakas, people so eager to make a living out of their hobby that became afraid of even trying something new. What the hell, if something works, just copy it! and then you have a legion of generic cliche mangas.

I seriously think that the manga landscape needs to do a deep cleansing to get rid of some of its basic and structural problems, and that probably means less mangas, or at least less clone mangas.

A superb article about the topic

http://io9.com/5874951/why-manga-publishing-is-dying-and-how-it-c ould-get-better

Poll's over. And can you believe it? This will be the last site poll chat box...

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A just ruler amongst tyrants

I believe those who say that past manga is better than current because it is not as trite is like a person saying anime is better than western animation for the same reason. It's not that there is less cliches, it's just that it's a completely different batch of cliche. I read series like Ghost Sweeper Mikami and series from Go Nagai and they also have cliches and archetypes that annoy me. Not to mention some of the characters from the classic manga, though iconic, tends to be very flat. Like Kenshiro from Hokuto no Ken, he's a good character, but you're not going to see him doubt himself or have some changing moment any time soon (except of course the flashback) he's going to do in one chapter the same he's done in all other chapters: Go in, see problem, fix it by killing enemies.

and as for the whole "moe" thing most of the better series I've seen tend to use the archetypical cuteness to elevate the narrative rather than detract from it.