Lucumo: The Legend of Heroes series is their biggest franchise. Ys is the most recognizable one, I agree.
"Huge" --> only owns PC stuff released in the West, pfff :P
This is why I was reluctant about creating a thread in the GOG General forum, nerd nitpicking... -_-
Their Legend of Heroes "series" is not even a series, it's a sub-series of Dragon Slayer (same as Xanadu), itself divided into metaseries (Trails in the Sky, Trails of Cold Steel, etc). I wouldn't call it their biggest series, it had been gaining reputation and a cult following outside of Japan in the past few years mostly because, well, it's the most "traditional Japanese" thing Falcom ever made, as it is the closest thing to what we in the West think of when we imagine a JRPG. Everything else Nihon Falcom made is real time, not turn-based, especially Ys and Dragon Slayer, which were created by Falcom as a response to the Western CRPG (Falcom wanted to make computer RPGs that weren't turn-based like Ultima or Wizardry). In fact, Dragon Slayer -- which spawned Xanadu and The Legend of Heroes -- is widely considered to be the very first action RPG, not even "AJRPG". I agree that a lot of people in the West have been crazy about Legend of Heroes games, as of late, but the fact still stands it's far from being Falcom's biggest (as in 'most recognizable') brand. Ys is and probably will remain their flagship franchise for years to come.
As for being a fan and "only owning PC stuff released in the West", what's wrong with that? I'm a person who enjoys playing video games, I'm not a collector for collecting's sake. I see no point in looking for Falcom games on eBay or import stores just to gather dust on a shelf, if I'm not able to play them. I don't understand Japanese, I can't read it or understand most of what's being said, so there's no point in buying Japanese releases of Falcom games. Plus, most of their older games, while indeed released for the PC, were out in the '80s, at a time when incompatibilities between hardware and software were even worse than today, and I don't own any Japanese PC of the time, in order to be able to play them, even if I did understand Japanese. I'm also not big on console gaming, the last console I owned was a Gamecube, and I'm not buying newer consoles just because of one or two games, so I stick to PC gaming, as I do need a PC for work reasons, so I might as well play games on it, as well.