EDIT: Sorry for all the grammar and spelling mistakes, I tried to get this done for you quickly! XD
There's so many different top ten lists out there! XD
Here's a few I found...
myanimelist.net/topmanga.php <So-so
thestar.com.my/lifestyle/story.asp?file=/2008/10/26/lifebookshelf/2350756&sec=lifebookshelf <That's pretty recent/good
comics.ign.com/articles/756/756462p2.html <And here's some way back from 2006, some of which are pretty good.
Really, it depends on where you go.
Honestly, the best places for the most
popular manga is where you can read it! NOTE: Popular doesn't always mean good, but there are definitely some good ones mixed in there depending on what you like.
These are probably the best 3 sites I know where you can read manga:
Manga Fox: My personal favorite--updates a lot and has hundreds, maybe thousands!
www.mangafox.com/Daily Manga: Another big one.
mangavolume.com/One Manga: NOTE: Mangas published by Tokyo Pop have been removed from this site because of *cough* some copyright issues. *cough* (--Actually, most internet mangas are self-translated/scanned by the sites which makes okay to put them up (somewhat/sort of--I don't know the rules for these kinds of things but from my experience nothing's ever happened... so I'm assuming it's okay! XD). In this case how ever, Tokyo Pop kindly asked them to not do it. So, no huge deal, really. Anyway, you can find the Tokyo Pop mangas on the other two sites usually...
www.onemanga.com/^All of the above have a top ten/top viewed list on the homepage somewhere.
The plus to these places is that, not only do you get to read the mangas, but the top ten lists are CONSTANTLY updated. It's really nice.
BUT BEWARE, of what you read... once in a while, you might stumble upon a manga with stuff in it that you never wanted to see... So, read the profiles (if there are any) first. *learned this from experience TT___TT* Usually, though, most/some mangas on the popular lists tend to be pretty safe. Just keep your eyes open. O___O If the title suggests things, then yeah... and if you don't understand what the title means, like I said, read the profile. ^^
So...
Finally on to recomendations! o:
I'll just recommend a bunch from all of the lists above.
--Train Man by Densha Otoku (A really sweet and cute romance, and short--only one book long)
--Death Note by Writer: Tsugumi Ohba / Artist: Takeshi Obata (MUST READ. *poke* *poke* *poke* A great detective/action/thriller. Read NOW. XD haha)
--Naruto by Kishimoto Masashi (Yes, yes, it been going on very long and come people think it's over rated... but It's SUPER popular so it must be a classic or something. Anyway, it's good, so, why not give it a try? It's about ninjas. XD)
--Bleach (Another SUPER popular one... that's newer at least. XD Although not that new, it's still very long. If anything though, I like this one better. This one's about a guy who can see could and then becomes a sort of soul reaper... it's good. I like it.)
--Vampire Knight by Hino Matsuri (I love this one. It's a mix between romance and thriller with vampires. I own the first two books in Japanese. So far, I love it. Another series by the same author is Meru Puri--MY FAVORITE. I LOVE this one. It's sort of a fairy-tale like romance with magic. This is definitely at the very top of my list.)
--Skip Beat! by Nakamure Yoshiki (Actually, I've never read this one but I've been wanting to for a long time. So I'm guessing it's good! XD)
--Hellsing by Kotah Hirano (Another that I haven't read but have been planning to read. ^^)
--Fullmetal Alchemist (a classic. Actually, the anime is better than the manga but it's still really good. ^^ about a short kid who travels with his brother, whose body is a suit of armor, and is one of the best alchemists around...)
--Beauty Pop by Arai Kiyoko (I also LOVE this one. It's about competing hairstylists. really funny with a touch of romance.)
--Ouran High School Host Club by Hatori Bisco (Funniest romanctic comedy/drama ever. Basically, they're hosts that find out this guy they have working for them is really a girl *not good for a host* and now they're on a mission to hide it... just started reading this one)
--Saiyuki *can't find the author for this one* (I don't know... lots of guns and stuff, but it's just so good. ^^ kinda hard to describe...)
Of course, I don't know if I can help you much with the popular lists since I haven't read all of them (and they're LONG so it's hard to keep up with like, 25 at a time XD), and because after I got acquainted with manga for my first time, I sort of found my niche and tend to hang around there. XD haha. Although, there a whole lot of popular ones that are on my "read next" list. So, I hope that helped! ^^