Manga Easily one of the best WSJ series at the moment.
I may be biased because I'm the guy who made this article and obsessively pimps it every week, but this is probably one of the best series in Weekly Shounen Jump. The concept is nothing that original- kid's childhood friend acts strange, disappears, and cryptically refers to things the main character is better off not knowing of. Ignoring said advice, he gets thrown into a Gantz-like game that seems to consist of nothing but running from place to place and surviving. However, it sets itself apart quickly by introducing several characters, and then having them all painfully die in the first few chapters (at least setting apart from Shounen in general. Gantz also shaved a cast down to nothing fast).
From there it takes a sort of modern speculative fiction angle, and many more characters are introduced. The series truly begins to flesh out with the introduction of the W.I.S.E., and the discovery of the DVD. Unlike most Shounen series, there is little emphasis on training arcs. While still there, they are generally one or two chapters, and less about becoming stronger to defeat the evil and more about having the tools to not painfully die.
Additionally, the fights include less Deus Ex Machina and power-ups, and more using powers wisely and effectively in order to outsmart the enemy. For example, the main character Ageha's power is unstable at best, and while incredibly powerful, will also attack anything with a PSI signature, including allies. So when he fights, not only does he rely on an ally so he can have time to program his power to do what he needs, he needs to calculate his ally's positioning when he releases the attack so that he doesn't kill them in the process.
The artwork starts off being kind of Bleach-ish, but eventually the anatomy gets better and is nowhere near as lazy as Kubo's style. He does fall into the trap of little-to-no backgrounds every now and then. But other than that, I consider Psyren to be a more grown-up Shounen and a breath of fresh air in the genre.
Manga Ensemble Darkhorse of Jump, Too Good to Last
You know what this series kind of reminds me of? The video game Earthbound (have not played the other games yet). It's a lot different from its contemporaries and overshadowed by more mainstream titles. Even their ability concepts are similar, with PSI attacks. Okay hackneyed comparison over.
My point is, Psyren really is quite a unique series. Sure you have your textbook hero Ageha, but he's not the idiot hero you've gotten used to with other popular Shonen. He's hot-blooded, but gains a great deal of maturity and isn't afraid to get his hands dirty. His foil is the heroine Amamiya, who isn't just cold to fit an archetype. While these two carry the series fairly well, the other characters get to develop as well. Cowardly Kabuto becames more serious and pacifist while retaining his comedic quirks. Iwashiro doesn't completely lose track of all his characters despite some of them not getting enough focus. Many of them have fairly integral roles; former antagonists Lan and Haruhiko turn out to be loyal allies, Hiryu and his group also come together to help, etc.
The main draw of the manga is the story, but it's kept interesting with the main conflict gradually expanding. First the goal is to simply make it through the game, but it expands to defeating the WISE and saving the planet. There is limited time as the present planning and future dystopia will eventually overlap. The prevailing theme of an uncertain future really engages the reader; what does it take to change the future, and change it for the better? The actual fight scenes are quite a sight. A mix strategies, twists, revelations of new abilities. You're left genuinely guessing for the outcome instead of simply "Oh his power is better/stronger, he'll win". Characters tend to have affinities but utilize them well.
There's action, ideologies, tidbits of romance, twists. Admittedly, it gets a little rushed at the end of the series (no doubt because of the changing ratings). It's recognizable as a Shonen, but...refined in sense.
It may sound like this is unbridled praise, but these traits are what really make it a shonen jump title that should have lasted a bit longer.
PS: I have not read Gantz so don't ask me to make comparisons