This here's the 3rd poll of the "Best" series! (More a popularity contest than anything though). Got one more to go after this...
If you really like seinen, I ask you to consider reading some of the suggested titles in this thread:
http://www.mangaupdates.com/showtopic.php?tid=13890

One interesting title that was suggested a few times is actually only a oneshot. For a short read that's good (to a lot of people), try out Hotel.

In case you were wondering about the runner-ups, here they are (in order):
Until Death Do Us Part
Gantz
Monster
Bitter Virgin
Black Lagoon


Josei
Next poll we're doing is for josei, so visit this thread here:
http://www.mangaupdates.com/showtopic.php?tid=13990


Previous Poll Results:
Question: Best Shoujo
Choices:
Skip Beat! - votes: 4023 (31.8%)
Ouran High School Host Club (Ouran Koukou Host Club) - votes: 3211 (25.4%)
Fruits Basket (Furuba) - votes: 2839 (22.4%)
Hana Kimi (Hanazakari no Kimitachi e) - votes: 1447 (11.4%)
Mars - votes: 1140 (9%)
There were 12660 total votes.
The poll ended: September 12th 2009

So yeah, Skip Beat! is the winner! (Personally, it's a series I love, so I don't mind it winning)

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A just ruler amongst tyrants

Mars is really underrated...

That's too bad, I really liked these. why no shoujo-ai, shounen-ai, or hentai?

if you are going by popularity shouldn't you take the whole of MU into consideration and use the MU popularity charts aka activity charts? only the more popular series get more activity.

I think if it were done that way then only ongoing series would be in the polls since those are the ones that get more activity. Unless it was done fairly and split into ongoing and completed series.

Interesting that all these Seinen series are ongoing. O_O

Yotsuba~ <3

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Monkeys, always at your service.

None of my 5 votes made it to the top 5, not even the top 10. Guess I am just not one for seinen. Will vote for yotsubato since it is the only one I actually enjoyed a bit.

Well...
I only like two of the seinen manga up there.
Yotsubato and Mushishi.
Voted for Yotsubato.
Historie is so underrated. T__T

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♪MONSTARR~ will eat all your cookies and steal your bishies~♪ Φ_Φ

I'm glad Yotsuba made it on the list. I wanted to give suggestions for this poll to get it on there, but I just don't read enough seinen.

with so many CRAZY Yotsuba fans in MU, i would be surprised if it didn't make it on the list. O_O

What's wrong with people here?!I'm not talking about best shounen OP,but best seinen xxxHolic, while Mushishi,and Yotsubato and Berserk are in the list....I'm scared of you, guys

also.Talking about seinen and no Asano Inio woks.Son, I'm dissapoint

I really wished Planetes would have made it in this... o.o
But it's not even in the runner-ups. D:

Oh well, my vote went to Mushishi.

just goes to show how the female vote is ruining the poll no guy in their right mind would vote for xxxholic as the best seinen with berserk and vagabond in there.

I am a male. Berserk isn't worth making the top 10 in my personal opinion.

sure.you are male, but just without balls.Nothing wrong with it