Well i saw Sign and was wondergin since there are many many titles about .hack, what is the main storyline, i mean after sign what should i watch?

.hack//legend of the twilight

Then after that, you could watch Roots, and play the PS2 games (Not the best, but not the worst games)

Really, all the ones after Sign carry on their own story lines. I doesn't exactly matter which one you watch.

Isn't the story line something like:

Games- Legend of Twilight- //Sign- Roots?

I liked Sign the best of them all, but I would recommend Roots if that's what you wanna see. If I remember right.. Sign is more talky, Roots is more actiony. I'm really not big on Twilight, the anime came across as very.. Saturday morning Cartoon-ish, and the manga was really short (3 vol.) and had a bad ending.

Don't have the games right now, at least i can play em on my ps3, might have a little trip to a friends house so i can borrow them, haseo looks awesome, pkk FTW!!!! reminded me of L2.

Really, all the ones after Sign carry on their own story lines. I doesn't exactly matter which one you watch.Yeah, I really hate the way they tied together the story between the R1 and R2 worlds.

"o btw someone set CC Corp on fire so now we gotta make a new game now lol"

hmmmm after .hack//sign? i suggest u watch .hack//roots

Actually, it would work best if you did this:
1.) Watch .hack//sign
2.) Watch the DVD included in .hack//Infection (or go on youtube if you brought a used game and the previous owner was too much of a jerk to include the disk)
3.) Play .hack//Infection, the first of four games that you can play and continue with the same level you had previous of that (so it is good not to lose your memory card and level up for the next sequal)
4.) Read the novel to .hack//Infection while you are playing, because I found out that there are some handy ideas of fighting techniques to use when facing bosses (just a hint)
5.) Play .hack//mutation, .hack//outbreak, and finally .hack//quaratine while watching the .hack//Liminality and reading the novels, if you want t buy them (I do :p )
6.) Rewatch .hack//sign, because chances are, it will make a lot more sense after you got the background from playing the .hack game series than from the first time you viewed it :p
7.) You can watch .hack//bracelet or purchase the manga, though it does not really tell you much about the mystery of "The World" and the commatose victims that .hack is centered upon, just a sequal to .hack for obsessed fans (sort of like me, heh)
8.) If you want to watch .hack//roots, its up to you, but the magic of .hack is pretty much lost, "The World" gone from a mysterious fire that destroyed it, and "The World 2" is created, still under the title of "The World." Now the "phases"
(like Skeith, who Haseo has--by the way, Haseo is Sora in .hack//sign, but he lost his memory after being data drained by Skieth and becoming part of his "red wand"--just a little irony for ya, details on wikipedia if your interested)
are used, not as enemies, but through a process called AIDA and what-not, and the only thing related to the original .hack is the commatose victims, which are called "Lost Ones" now. The game, .hack//GU, helps understand .hack//Roots better, but I only watched some of .hack//Roots and played the first game, so yeah, not too much info on this one.

Well, hope that helps a bit. To summarize, .hack//sign and the first dot hack game series were the keys that tied to the mystery of "The World," and the others are just sequals to keep .hack fans entertained. oO If you think I am obsessed, I encountered someone online who memorized the whole Epitaph of Twilight (aka what "The World" is based off of)

T_T yes, I have no life...