Naruto is a work that creates a lot of hysteria both ways due to its popularity. Whether people like or dislike it, they all feel compelled to talk about it. While I think a lot of people can come to the casual, and really accurate conclusion, that the manga started out as a much more fun work than it has come to be, I do not think a lot of people understand exactly why, which is what I want to address. Some spoilers of course, since I cannot really talk about the problems of this manga without talking about Pain.

I felt like this was an 8/10 manga at the start (add in the 4/10 it has been for the last 200 chapters, and a 4/10). While there were MOUNDS of angst, a fairly typical "training arc" layout, and a fairly typical foundation for the type of cool characters (ninjas), there were a lot of positive factors that more than made up for any of those problems. Kakashi taunting his students with his erotic book and the exaggerated responses that come in return (ch.5 p.5) are a good example of the fun spirited nature at the beginning of this work. The aspiration that was evident for Naruto helped keep the story very lighthearted despite Naruto being a brat, Sasuke being a grim angsty boy, and Sakura being a typically feckless cling-on girl character. When you replace that aspiration with "I have to save my friends! Everything is so terrible!", the manga loses a certain amount of its fun spiritedness, and I think the people involved with making this never really thought that out properly.

Now I am not saying the start was perfect, for instance the lack of backgrounds all over the place (just look at say practically any page in chapter 23), but the side characters all have real personalities, the powers are mostly very well thought out, and the battle action is very cool indeed. Things that were lost in the anime like how striking Naruto looks when the nine-tails starts taking control are completely impressive and one of the reasons that reading this manga was so fun. The tournament was completely mainline shounen battle manga fun, and while it is not the most original storyline or even action ever, it was just as fun as any of those has ever been, a definite high point for the manga. There are certainly still good storylines and fights afterward, for instance I would say the puppet master fight is a relative high point, but a lot of problems started to become endemic.

I think it is pretty obvious that a lot of the reasons for the changes in Narutos were the trappings of its immense popularity. With pressure and popularity comes a need to make every character cooler, to appeal to broader audiences, and to simplify plot aspects. In this case it is also pretty evident that there became a real sense of needing to be taken seriously, so we get to slog through a lot of grim angst rather than fun spirited adventure or expressiveness, and it has been that way for something around 200 chapters. While there certainly are works that are grim and work, the people involved in Naruto unfortunately do not have the aptitude to write that sort of dialogue or draw that sort of art. As the villains had to become more powerful and the plot "more epic", the art simplified in shading and character forms, which has been a big disappointment for me. The overall construction of arcs weakened too, and the humor has been just basically completely lost (with the Bee and Naruto's interactions being a great example of just terribly executed gags).

None of the above was really enough of a breaking point for me to stop reading the manga, but Pain was. When you implement a plot copout like killing off a large portion of the characters that we are supposed to care about and then revive all of them, you have cheapened the plot in a way that a work can never really recover from. Pain's transformation to senseless hate to incredible generosity happens in such a short span of time that it is not really very compelling anyway. Even then I picked the manga back up, but what was enough to drop it for good was the recent spate of grim faced unhappiness (personified by Sai), overbold art style (a la Bleach too much ink), or bad attempts at introducing mind game oneupmanship (Danzou) wearing on me to the point that this manga just was not a fun read anymore. It has lost all the fun, and if you are attached enough to the characters then I guess it might still be worth a read, but I would honestly recommend that the end of the fights with Orochimaru is probably the best place to drop this manga if you start to feel like you have had enough. Feel free to stick with Naruto and Sakura trying to prove how adult they are while sobbing about Sasuke a lot though.