They were big in Japan, but it took a while longer for them to catch on in the US; IIRC they didn't really become a big thing stateside until 1993-94 (i.e. the point when SNES RPGs started getting really, really good.)
Still, it probably does have more to do with regional barriers than timing; after all, Western-style RPGs were pretty big during the Amiga period, so you'd think they would have at least brought over a couple of the more popular JRPGs to see if they'd sell (heck, non-MSX home computers are practically the only platform they didn't port Dragon Warrior to.)
Dragon Quest originated on the MSX and was released simultaneously for the NES. Thats it.
JRPGs were definitely popular before the SNES days. Nintendo Power pre SNES proves this.
The problem is that the computer RPG scene in the western world was radically different than the console one.
Ultima vs. Dragon Warrior, for example. Totally different gameplay concepts.
Alot of heavy CRPG players I know dont like the linear qualities of JRPGs.
and you'll notice there are not alot of first person Japanese RPGs, and the ones that do exist (Dungeon Magic!) are kind of strange in comparison to Western ones like Goldbox games and Might and Magic.
Given the time the Amiga was released, they really should have tried getting a few games to test the waters. Dragon Quest 1, Final Fantasy 1, and Ys would have been good tests to see how things would have went.
also, fishy_fiz, you need to play Wasteland, asap. Though I recommend it for DOS unless you like dealing with disk swapping. Never playing that game is like, against the rules of life.