Actually Terranigma made it out of Japan. It just never saw the light of day in the US.
Anyways, the thing about a lot of SuperNES era JRPGs is that a number of the good ones that we've missed have already seen ports and remakes on different consoles since then. Front Mission is on the DS, same with DQs V and VI, even the first Shiren the Wanderer and a remake of the first book of Fire Emblem 3 are on there. Romancing Saga 1 can be found on the PS2 while the PSP is home to port of Star Ocean 1 and a vastly superior version of Ys 3, the Vita will hopefully be home to Falcom's actual take on Ys IV, and the PSX saw the release of Tactics Ogre, and along with the GBA, a port of FFV. Also on the GBA is the only western released version of Tales of Phantasia.
As for the games that haven't seen an official release but have been translated....
Mystic Ark (7th Saga 2)
Bahamut Lagoon (try to play this)
BS Zelda (at least Ancient Stone Tablets)
Far East of Eden Zero
Fire Emblems IV and V (III hasn't had a proper translation done yet but a translation patch for the DS remake of 3's Book 2 and the BSFE chapters, basically the parts we're still missing, is being worked on even as we speak and probably the way to play versus on the SuperNES)
Front Mission: Gun Hazard (don't expect to be playing an SRPG though as it's far more like Assault Suits Valken than Front Mission)
Gunman's Proof (decent Zelda clone)
Lady Stalker (if you liked Land Stalker)
Lennus II (heard good things about this, basically Paladin's Quest 2)
Live A Live (fun little game that's also a painful reminder of what we lost when Squaresoft became Squeenix)
Metal Max 2, Returns (among the best open ended JRPGs ever made, have received remakes on the DS but it's easier to get patches for the SuperNES versions, get these)
Romancing Sagas 2 and 3 (if you can handle them, get them, 2 the better of the two)
The Adventure of Hourai Highschool (made before every fucking anime on the planet became set in a highschool setting, fun game with an FFV like job system)
Treasure Hunter G (worth it if you like Sting games, has no relation to Dept. Heaven though so don't look for that)
Treasure of the Rudras (another Squaresoft oddity from back when they still made games, worth checking out at least)
I'm going to comment here that I wouldn't bother to go looking for the SuperNES SRW games as they lack a great deal of the conveniences that more recent games enjoy and thus are kinda rather hard to play through.
There are other games as well but I don't know their quality or how well they stand up today, and many of which were fairly derivative of Dragon Quest and the like so there are a lot of them that wouldn't really offer you anything new at this point anyways and are safely skipable.