You're overselling it. Tales, Dragon Quest and Earthbound are only cult hits, Mario RPGs are a spin-off of a hugely successful franchise, Kingdom Hearts is a spinoff of another hugely successful franchise, and Pokemon is technically an RPG but people rarely think of it as one. When it comes to RPGs that are popular in the West, on their own merits, you really just have: Final Fantasy, Persona, Xenoblade, Fire Emblem. And note that, aside from Final Fantasy, those are all fairly recent breakthroughs (last decade).RPG's are still very popular in the west, Pokémon, Final Fantasy, Tales, Dragon Quest, Mario & Luigi (Paper Mario, too), Earthbound, Xenogears (and Xenoblade), Persona, Kingdom Hearts, Fire Emblem, the list does go on.
To reiterate: not well. A new IP in a niche genre released in the last days of the console's lifespan is not conductive to success.The thread isn't on whether WRPG's are better than JRPG's, it's about how well Tales of Phantasia would have sold in the US had it been localised for the Super Nintendo.
Frankly, for Tales to be a success in the West, you either need 1) a slow, steady build to a latter-day success, circa now; 2) a complete restructuring of the series' developmental schedule that allows it to better complement overseas releases; or 3) a miracle.