>>15095673
>R1
In order accessible, preferably if you ask me. However, .hack//Sign isn't for everyone, namely due to being fairly low on action and high on dialogue and character interaction (thus actually understanding a lot of what happens of interest in MMOs is communication). It does do a good job of showing the sorts of people attracted to MMOs, and has a great OST. At the same time, it's worth considering that Sign is in effect background and world building for IMOQ. One can play IMOQ without necessarily needing to watch Sign. But one who watches Sign without playing the games will have a lot of the questions raised go unanswered.
>R2
Roots does serve as background and base characterization, namely for Haseo's drive and how he knows certain characters in the G.U. games. It does have the issue for some though that it goes too hard and too long on the EDGE (despite his hunting of PKers being a coping mechanism since at that point he actually can't do shit himself to help the situation), and in late parts has spoilers for Volume 2 stuff before it even happens. Again, not absolutely required to watch, but it again provides world building and prologue, some events of which the games both gloss over or assume the player has watched. And watching the anime without playing the games results in a kind of depressing outcome where nothing done really had any benefit (which the games continue from). Did like seeing how much Phyllo's real life death devastated Haseo in the last episode or so, being so focused on revenge he didn't even know the guy had died, nor realized just how much he'd come to like the old man's advice.
>>15095973
Link has a fan-translation that's nearly done, at least last I checked. Haven't especially seen positive reception towards the game from anons though, but again, it not being patched yet limits the western player base, so perhaps those that dislike it are more vocal.
>>15095959
I played them back to back just fine. I just didn't try to 100% each volume (which are handled in such a way to kill time when it was months between volumes being released, whereas now one can have access to all the games and just continue the story without delay). But yes, I'd wager going for competition back to back would be very tiresome.