I'm about to catch up to Vinland Saga, I'm at chapter 176
it was pretty good, but I wouldn't consider it one of the greatest ones of all time

The art is very good but there are a lot of panels that look like this (notice the background) which isn't bad or anything, it's totally understandable for a mangaka to save time and effort by not drawing all the unnecessary settings of the backgrounds in every panel, but most of the mangas that are considered to have the best artworks of all time rarely look like this (Berserk, Goodnight Punpun, Vagabond, One Punch Man...) and I think not criticizing Vinland Saga for these panels would be unfair to mangakas that actually put in all the time and effort to make a manga look THAT good.

Now the story:
The moment Thorfinn finally unites with his long lost family is reduced to a ridiculous comedy sequence with Ylva punching and choking Thorfinn, I was looking forward to this moment for so many chapters and it was such a let down

After a certain point the story gets kinda soft, the first half is FULL of rape, slaughter and stealing, and the fact that the manga never held back was very impressive to me but after Thorfinn goes through his development it's like the world around him gets a little softer too, the last actually tragic thing that happened was Arnheid's death (the pretty slave girl that Einar was in love with).
Halfdan does pretty much nothing after his son's bride was "stolen" by Thorfinn even though he was known for being a weasel who takes advantage of every opportunity to strip people of their wealth and "chain" them, Thorkell let's Thorfinn go without having a duel just because Gudrid (the girl who always snuck in Leif's ship and wanted to see the world) made a fuss even though he seeks nothing in life except battle.

There are a bunch of stuff in the story that didn't make sense to me, the biggest one being Thorfinn's entire conviction, it sounds kind of childish.
let's say he did succeed in making a land of peace in Vinland, the rumor would get around and warriors would come to ravage it and they wouldn't be able to defend themselves.
if this was One Piece, a conviction like that would be totally fine because One Piece is the kind of story where everybody is kind-hearted and actually seeking a land of peace would make sense in it, but when you have multiple scenes of the main character and his companions slaughtering the living soul out of an entire village it's clear you're not taking the kind-hearted "One Piece" approach to storytelling, it's clear you're taking a more grim and realistic one.

There's little character development aside from Thorfinn, and Canute, the rest of them remain pretty much unchanged (or in the case of Ylva and Sigurd their sole purpose becomes comic relief which I'm afraid is even worse, it happened to Puck in Berserk too)
And even Thorfinn's development could have been MUCH better, the way he deals with his thirst for vengeance isn't really polished, we see him as a bloodthirsty warrior and the story just cuts to him being a depressed slave.
We see Canute seeing his father's head everywhere he goes and his father is telling him that he too is becoming a slave to the crown, but after Canute and Thorfinn's exchange we don't really see Canute's father's head coming back.

The first 16, 17 volumes were awesome, I genuinely thought it would end up as my favorite manga of all time and a perfect 10/10 but I can't give it anything over an 8 (I still don't consider it to be bad, like I said it was pretty good, there are a lot of things to love about Vinland Saga, like its historical accuracy and attention to detail)

Also, I thought the two year skip of their voyage to Greece was a very poor choice I was looking forward to seeing 11th century Greece drawn by Yukimura and seeing the characters communicate with foreigners.

p.s: I posted this on Reddit and a bunch of very nice folk changed my mind about Vinland Saga, it is now a 95 for me, and a masterful work of art.
here's a link to that post