This could've been a 6, maybe even a 7 depending how the ending went but, sadly, that was not the case. This review will contain spoilers, particularly about the ending however, what you at LEAST need to know that isn't a spoiler is, if you watch this anime, expect to have to play the games to get all the answers and possibly also watch the other anime in the franchise for any remaining ones and even then I cannot assure you you'll have all the mysteries solved as i have not played any game or seen any anime besides this one. I have however taken a look at stuff which tells me this is likely the only way you're going to get the answers you seek at the end of this season and episode 27 and 28 of this series... (Though someone claimed some of the answers but not all are answered in .hack//Legend Of The Twilight, cannot say if true or not...)
Now, onto the review but as i said spoilers will be mentioned.
.hack//Sign is an anime that has not aged well, I'd argue however it wasn't even good back in the day either and yet, somehow it draws you in. The mystery is nothing special and the writing is honestly bad. Lots of times the anime will simply skip parts so a character or a group of characters will be in one place both during and at the end of the episode, and the next thing they're suddenly in another place, not having shown or continued from where it left off both during and at the start of the episode. The acting in both the sub and Dub is good (I didn't watch the sub much, but what little I saw was as good as the dub) but thanks to the writing, the characters often enough speak in a slow or unrealistic manner, same with their actions. Speaking of action... do not expect to see much of that at all, despite being an MMORPG VR game, the battles are laughable, I swear so many compare this to SAO but none ever ONCE compare it to Spice and Wolf, which it shares FAR MORE in common with in the sense of its mostly just characters talking but unlike Spice and Wolf, .hack//Sign is not even CLOSE to being on the same lv of how GREAT that anime is. SAO it shares a few themes with but honestly, a LOT of anime shares similar themes (Especially these days with so many VR game anime popping up left and right) and in case you're wondering, there is NO comparison for how GOOD SAO is compared to this one. Sure I like SAO and will admit it has its own faults (many i fact) but if you're comparing the two as many have prolly done, SAO is the superior anime/series/franchise here hands down. Bonus points that you DON'T need to play a SINGLE SAO game to understand whats going on and have the mysteries solved for you :P
I normally never make comparisons to other anime when i review an anime unless its one in the series of the anime am reviewing, however, since a lot have made comparisons to SAO and seeing as this is likely the 1st trapped in a VR game world or one of the 1sts odds are, I felt it was needed to make those 2 comparisons. (Fyi, Spice and Wolf is FAR superior to this, even though its mostly talking its night and day difference between it and .hack//Sign)
Anyway, that's enough of the comparison. I'll just say this, as I said at the start of this review, this could've been a 6 or even a 7 depending on the ending, and by now you might've guessed WHY it's rated a 4.0. That is because at the end, the anime just ends... abruptly... The enemy would NOT log them out, yet that's what the anime seems to indicate happened... I suspect its a fake world and they're still in The World but alas, I'll not know unless I talk to a friend who knows, go read up on a wiki or go play the game(s) and if your viewer base has to do ANY of that, you have sadly, succeeded at something that NO writer should EVER make a reality as it turns the viewer off, it ruins it for anime only watchers and I say this not lightly because .hack//Sign left MANY MANY questions UNANSWERED on TOP of that abrupt ending! Again, this is what we call bad writing. The worst part of this is knowing they had EVERY opportunity to answer every question but they seemingly don't and that's made worse when they made more and more anime series in this franchise but didn't bother to properly continue this in the anime. (.hack//Legend Of The Twilight "might" answer some of this but since its focus is on two characters not in the Sign anime and has them playing as avatars based on the look a like Tsukasa and Mimiru called Kite and Black Rose respectively, it is unlikely this would continue the story with the Sign characters and even then you'd need knowledge of Kite and Black Rose possibly from the game(s) to fully enjoy that anime...)
It goes without saying but, even if the games are available to play (Which i doubt) I wouldn't be interested in playing them, especially when the anime's writing and animation were so laughably bad and unrealistic and as an anime only fan of this anime, i guess that means my friend and or a wiki is my only option for knowing what the anime SHOULD have told us. Like I said before, .hack//Sign somehow draws its viewers in, despite how bad it is but, it really did get lucky to release when it did, as bac then it was better as not many if any did what it did, however, that still doesn't make it a good anime/series and somehow it gained many games, anime and more. That just shows you how important timing is for when you release something as you know this wouldn't have gotten a sequel much less a game (and if it did not more than 1) if this had released in this day with modern art but the same style of animation and lastly, while the mysteries are what will likely keep you hooked, the stuff they DID answer was honestly, meh to bad. Totally not worth watching is my take on this but who knows, maybe you'll like it? Hopefully this review helped you to decide if you wanna watch it or not.
Oh, bonus round! You thought we were done? Nah lol Sora says: Oh, looook, later series and games made look a likes who look like Tsukasa, Mimiru, Bear etc. but are not them. THAT'S not confusing especially for kids~
P.s. This reviewer as said hasn't played the games nor seen any other anime, if anything I've said here is wrong my apologies but this SHOWS at the very least how jumbled up, confused the anime only viewers will be thanks to how they told the series' story and that as said is bad.