Obviously the Regal Mammoth and Century Soup arcs were the stand out introductory stories that got everyone hooked on the series. I think that was the peak for many people. The Ozone Herb and Melk Stardust parts were good for character development of the 2 main protagonists, but lacked the impact and intensity of the previous larger arcs. Mellow cola arc was solid, but was pretty much supported by the introduction of Zebra who brought a refreshing dynamic being so different in character to Coco and Sunny.
For me, the Meteor Garlic Arc was a return to greatness. That card game was probably my favorite part of the series and felt reminiscent of the battle with D'Arby in JoJo. I was literally on the edge of my seat wondering how it would end!
The Bubble Fruit Arc was again a bit lack luster and like many have said, this is when things started getting weird with the introduction of "Food Honour".
The Four Beast Arc would have probably made a suitable end, except for the threat of Midora and the Bishokukai and the need for Toriko to "conquer" the Gormet World and complete his Full Course.
The Cooking Festival Arc was a mess, the introduction of "NEO" unnecessary and the off-screening of Coco Vs Grinpatch disappointing. I started to struggle at this point and whilst still a fantastic manga, it was clear it would never return to it's greatness of the earlier arcs.
Shima knew it, his editors knew it, damn even Toei knew is, (that's why they pulled the plug).
In my eyes, the timeskip was an attempt to fix things, but by this point the creative juices had stop flowing (or begun overflowing depending how you look at it), the world of Toriko just started becoming more and more ridiculous, with the laws of physics and reality being more and more warped to the point it became a parody, and Shima decided to run with it, giving us characters like Bambina and Don Slime to fuel the nonsense.
I guess he was trying to make the Gourmet World exciting (like Alice In Wonderland style), but unfortunately as a reader I became disconnected with the story since there was no longer any semblance of reality and everything turned into a "anything can happen" scenario.
Now don't get me wrong Toriko is still on my top 3 of all time list and these flaws are by no means limited to this series alone, every great shonen has it's faults and i'm only nitpicking because this could have been the greatest Shonen of all time.
For me it's up there will Dragon Ball and One Piece, with Kinnikuman a very close 4th. (We need a new anime!)