I don't know what mainstream means for you, but if it's a manga which garners public attention at a large level then:-
First out of the ones you pointed out:-
1.Hunterx Hunter:- For me it is one of the best shonen(well actually a seinen pretending to be a shonen =D), it has one of the best character development, plot development, world development and overall story pacing, it's absolute best.
Now comes the fix, art depends on Togashi's mood it can range from just brilliant to abysmal and Hiatuses.
If you are a patient then go for it the reward are huge, if you aren't then watch the anime.
2.Toriko-Has one of the best world development and brisk arc pacing, art and story cohesion are good. You can easily make it a weekly quick read, will alway pay.
3.Katekyo hitman reborn- From the limited info I have on it I can say artstyle is good and action is ample, i haven't fully read it.
Some more suggestions:-
Berserk
Vagabond
Nanatsu no tarzai
One punch man
AOT
Tokyo Ghoul
Boku no Hero Academy
Older one's:-
YYH
Slam Dunk
City Hunter
Rurouni Kenshin
Fullmetal Alchemist
Death Note
I hope these will keep you engaged for some time.
