The Unknown
Pokemon is super long (over a 1,000 episodes I believe) but it isn't very good by any stretch of the imagination .
If a tree falls in the forest and nobody remembers it, who else will you have ice cream with?
It would be easier to give recommendations if you're looking for something in particular, besides just being long.
I would honestly suggest the opposite. There are short series (24-episodes, or even 12-episodes) that are pure gold.
A Wannabe Writer
The Other Wiki has a list
if you're just looking at sheer length.
As for recommendations, you mentioned not wanting "kid shows" but beyond that I have no idea. Maybe all the Dragon Ball stuff, since you've already seen One Piece?
(And I've heard good things about Doraemon, but I've never seen it)
edited 9th Jul '15 10:42:20 AM by Watchtower
The Unknown
Looks like I was off about Pokemon, but over 700 total is still huge.
If a tree falls in the forest and nobody remembers it, who else will you have ice cream with?
![[up]](https://static.tvtropes.org/pmwiki/pub/smiles/arrow_up.png "[up]"){kind=icon}
Thanks for that.
I can handle all genres, so I just referenced to anything long.
I've personally not seen it for more than a couple of episodes and honestly don't plan to watch past that, but has Bleach crossed your mind?
edited 9th Jul '15 11:41:48 AM by Nickpws
Professional Moldy Fig/Curmudgeon
There's a lot of really long-running anime, but much of it has never made it outside of Japan, and much of it also doesn't cater to Western anime fans' taste so you'll never see it here, either. (It's kinda surreal that Doraemon made it here...)
I suggest you try some that are, maybe, 52 to 100 episodes if you want anime with a lot of episodes.
"They say I'm old fashioned, and live in the past, but sometimes I think progress progresses too fast."
I'm not insane, I'm not… not insane!
Both Fullmetal Alchemist series are good I would say (it's 51 and 64 episodes I think?), don't know if they're long enough for you.
Flippé de participer à ce grand souper, je veux juste m'occuper de taper mon propre tempo.
I am now a shiny stone~
The longest runner is Doraemon.
The three finest things in life are to splat your enemies, drive them from their turf, and hear their lamentations as their rank falls!
LET'S BE FRIENDS!
Anyone here ever thought of Detective Conan? :D
It's all about Anime, Manga, Comic, Cartoon, Sci-fi and Cosplay! Get the social app now: http://bit.ly/saikoplus
A Wannabe Writer
It's right in the first post, mate. 
LET'S BE FRIENDS!
Oh yeah it's there, thank you! This series seem long, but I love it! Hihi~
It's all about Anime, Manga, Comic, Cartoon, Sci-fi and Cosplay! Get the social app now: http://bit.ly/saikoplus
Given our definitions of "long" might differ, Yu Yu Hakusho was somewhere in the 200+ range. Yu Yu Hakusho is basically a shorter, more cohesive Bleach if you ask me.
I'M MR. MEESEEKS, LOOK AT ME!
NaNo 4328 / 50,000
I usually like to watch anime with many episodes. This started when I wanted to watch One Piece and ever since I always desired for something as long. I checked and the only other show that doesn't seem to be a children's cartoon seem to be Detective Conan.
However, it doesn't need to be one series. If one combine a whole franchise you tend to get enough episodes. Like Naruto and Naruto Shippudden together is more than 500 episodes. All Captain Harlock shows is more than 248 episodes. Gundam is 800 episodes, which is very nice.
Are there more suggestions of this sorts? I've already watched OP, Naruto, Captain Harlock and I'm planning to watch DC.
Is Doraemon any good? It seem to be the only children's cartoon worth watching.
edited 9th Jul '15 10:21:55 AM by One_Island