Manga huh? One of my favourite forms of procrastination... I could go on all day about this!
I don't know why people like Bleach that much. It was freaking awesome for the first hundred or so chapters, but then when we started journeying through Hueco Mundo, it kinda abandoned all the interesting themes in favour of engineering this hugely overwrought supervillain that you know, a hundred chapters in advance, needs to fall by the hands of Ichigo's thrice-upgraded getsuga tensho. Aizen isn't even all that good a villain, he's merely annoying with a neverending litany of conceited posturings, like one of those really stinky farts that you can't stand but simply have to wait and tolerate because you know he'll go away eventually. If the author had done more to explore the history between the Shinigami and Quincy, or examined in more detail the role of Urahara and the forming of the Hongkyu, or simply showed us more of Yoruichi (lol), instead of funneling it down to this monotonous singularity, then yeah, I would have remained a big fan. Not surprisingly, quite a few of the die-hard fans I know agree with this assessment.
Naruto is moving along fairly nicely again after a bit of a sump. While Uchiha Madara is the singular villain of the plot, he's nowhere near as invulnerable as Aizen was, and the shifting politics between the villages and the various missing nin groups (e.g. Akatsuki) is actually a genuinely interesting dynamic. Naruto, too, is developing well and of the Shonen Jump! titles currently running, this has to be one of the best examples of the genre as far as character development goes.
I'd also like to say I'm a fan of Hunter x Hunter but that's in the same place as Bleach is, only I suspect the author of HxH is far more tortured over his quandary, which is why he keeps going on extended holidays every three chapters. Worse, "the King of the chimera ants" (Meryem), looks awfully similar to Cell from Dragonball Z. Whoops. Still, when it does go, it's dark and gritty the plot doesn't pull any punches.
Speaking of dark and gritty, there's Beserk, but I really don't think I should be talking about that manga on a PG-13 forum. Same applies to Jackals, which is in a similar vein, except instead of demons you have mafia-like gangsters.
I like Initial D and Hajime No Ippo purely because they're relevant to my interests. However, the manga Initial D is very preoccupied with car mechanics and driver theory, and often spends a whole volume on pages of cars driving on mountainside with a few bits of dialogue consisting either of "his driving theory is perfect" "OH NO WAIT IT'S NOT!", or "because the car's weight is shifted to the rear in the drift Takumi is able to hang the front wheel over the gutter and shave even closer to the apex of the turn!!!" "OH NO I CAN'T HANDLE HIS AWESOMENESS". It got a bit samey after a while. As for Hajime No Ippo, think the same thing, except with boxers... and far funnier characters, thank goodness for that! Just as well the anime versions of those only contain a fraction of the plot.
Bobobo-bo-bo-bobo actually rates pretty highly on my list because it is so friggin' random... I only get a fraction of the puns in it, which is a shame, but nonetheless it never fails to have me ROFL. However I can't read more than two or three chapters at a time, otherwise I get utterly lost.
But my favourite? I'm a One Piece guy. Yes, I know it's about pirates, foresworn enemy to ninja. It's what convinced me that I shouldn't be so anti-pirate. In fact, it's what convinced me to buy a shirt that says "I support the ninja-pirate alliance." I can't fault Oda's work. Sure the plot's rather complicated and big and the action and the characters are utterly ridiculous but that's why the work is so epic. The pacing, the comedy is just right, and the ideal of stubbornly pursuing one's dream while forging unbreakable friendships is actually quite moving.
Very similar to that and therefore not far behind is Great Teacher Onizuka. I never thought I would approve of stupidity, but Onizuka's special.
fighting and gore..and women... what else do u need?
If that's all you want in a manga, I would recommend you read
Tenjho Tenge... but don't tell anybody I told you that >_> Also the ending is nearly as weird as the
End of Evangelion films. If you want something a little milder,
History's Strongest Disciple Kenichi is a popular choice. Personally I don't care too much for the copious amounts of
ecchi in both. For something a little different, try the
manwha (Korean manga),
Veritas, as the plot for that is pretty interesting.