1. Black Clover
2. David
3. One Piece
4. Jujutsu
5. Hero Academia
Later I'll go to deeper detail
Time to explain myself:
1. Black Clover: Elfed Arc is current best arc in Shonen Jump for me, Is being way superior to Wano Arc or MHA current arcs. Everybody is shining, a lot of plot-twists, of epic fights, of character development (Noelle, Zora, even Nozel). Elfed Arc is the very definition of how a shonen arc must be done, is so perfect.
2. David-kun: Didn't enjoy a comedy series in a while. For me, is being already superior to Saiki and it has only 14 chapters so far. Love the interaction between characters (Mona Lisa is gold), and all these art references. I think is going to be a solid success.
3. One Piece: while I didn't enjoy Big Mom arc so much, Reverie and Wano are being very enjoyable so far. I think Wano is being the best OP post-timeskip arc, and I'm very hyped for what's coming next.
4. Jujutsu Kaisen: the big surprise of 2018, already selling more than Dr.Stone or BokuBen. Since chapter 10 it has been in a constant growth. Lot of interesting and very enjoyable characters (Itadori, Gojou, Nanamin), and a heavy plot (look at what happened last arc). Still needs to be more polished but in only one year it has had the most solid start since Neverland. Want to see what 2019 brings to Jujutsu.
5. My Hero Academia: I'll start saying this current arc is weak, possibly the weakest arc of the series. But at the same time the Pro Arc has been for me the best arc of the series, and it was refreshing to see an arc in which the protagonists weren't the students or All Might, but Endeavor and Hawks (I'd say Pro Arc has been the second best Jump arc of 2018 after Black Clover Elfed Arc). Also, the Culture Festival was enjoyable (Gentle was a totally different villain in comparison with rest of villains). Seems 2019 is going to be strong after that teasing in this week chapter.
I've been debating myself between Hero Academia and Kimetsu no Yaiba for the 5th place. It has been hard.
PD: At the same time I see worst Jump title for me has been
Shokugeki. It just has turned into a mess.