>>1706940Arise isn't a prequel and also is garbage. Skip it, although it has a couple of neat cyborg fight scenes.
>>1702588There are three separate continuities for the anime/films.
The first is Mamuro Oshii's two films, Ghost in the Shell and Ghost in the Shell 2: Innocence. They're both pretty slow-going and more philosophical and are both worth watching, although Ghost in the Shell is better than Innocence.
The second continuity is the Stand Alone Complex continuity, which is more of a postcyberpunk police procedural than a slow contemplative film about whether or not cyborgs/robots have souls, although the philosophical stuff pops up a fair bit in places (especially in the second series). SAC has two full series (Stand Alone Complex, and 2nd GIG) and a film (Solid State Society) and they are all worth watching.
The third continuity is the recent reboot OVA series, Arise, where the Major is 20 and spends her time getting hacked instead of being badass and it's just kind of shit. Skip it.
The three are completely separate continuities and don't connect at all. They are also separate from the manga (which I wouldn't bother with; Masamune Shirow is a creepy pervert and the tone is very different from the films/SAC, even though the first Oshii GitS film is a loose adaptation of the manga). The sequel manga, Man-Machine Interface, is just straight up crap.
There haven't been any GitS video games in a while, and none of them had any plot that officially plugged in to the series.
tl;dr watch Ghost in the Shell and Innocence (the Oshii films), then watch the whole of Stand Alone Complex (SAC, 2nd GIG, Solid State Society), then be sad that Arise is shit.
