I agree we shouldn't decide what's good or bad.
But we also shouldn't tell people what they SHOULD be translating.
I am currently playing the original Megaten. Befriending enemies was a pretty new (for console games, it probably wasn't the first as I heard Wizardry 4 did that earlier. But I never played a Wizardry aside from renting the SNES port of 5 a few times as a kid). Certainly historically important since it launched one of the largest RPG franchises. But there's honestly a few things I have no qualms save-stating for (and I normally try to play games without tool assistance.)
I've been starting to play Metal Max in Japanese. I would like to try to work on that, as Gideon says he has no interest in the original version. I'm sure the SFC version is probably better but for a series that has managed to keep running so long, it's probably historically important to have the original translated.
Akuma-kun is a rather short game, but I'd say it's decent. Probably even shorter on replays since once you learn a new spell (most are learned by level-up) you can get a recipe to quickly re-learn it in another game.
Momogaiden is also in the works. I'd work on the FC version because it's what I'm most used to. I don't know if PCE version would be easier to translate or not. mednafen's debugger is certainly powerful but not very easy to use. I also wouldn't be surprised if it was more heavily compressed (I know Momotarou Densetsu Turbo is Huffman compressed, compared to the FC original which is actually uncompressed but stored its text in 7 bits per character encoding instead of the normal 8 bits. MDT is still worth its own translation as it diverges pretty heavily from the original version.
Dungeon Kid I think stores its text as 16x16 metatiles (or TSA, I think they're often called by ROM hackers). Also, a top-quality hack would probably modify the SRAM format to store double-length items, enemies, or whatever (as I recall, it was already storing the dakuten as separate bytes, so it is certainly exploitable to store expanded names).
I had worked on Satomi Hakkenden before. I'd like to finish, but I had to basically rewrite the text engine (and would have to fix the resulting broken windows).
I think Last Armageddon is different between systems, but I haven't played very much. PC-98 seems to be a dungeon crawler but the FC version seems to use a FF2-like level system.