With all due respect...I wouldn't call the Fostex G series a compromised machine compared to the Tascam MSR 16...both sound about the same, with just the difference in NR...but AFA functionality, the Fostex w/8330 sync card onboard, was much more robust...and it had pro-level options, in a small-format deck.
Had mine for over 20 years before I moved to the 2" format...never had an issue with anything on the machine, it always worked flawlessly...still, these are all small-format, and none of them measure up to the large-format decks.
The E16 was also solid deck, but didn't have as much functionality as the G series. I can't really speak about the earlier B series.
The reason Tascam gets the lion's share of that small format market...is due mostly to them being around a lot longer, as Teac and then as Tascam...so they churned out a lot more gear, which meant a lot more users.
The Fostex G series came out during the last days of analog tape use as the main medium, especially in the project and early home studios...and then ADAT came along, and that helped kill off the tape decks in those types of studios, since it promised the digital benefits, though ADAT generally sucked overall...and while it lasted for a good period, it vanished along with the company the introduced them, Alesis.
I think if the digital stuff held off for another 5-10 years, the Fostex tape decks would have gained a much greater fan base...but I still don't think they would have equaled Teac/Tascam, which was already way ahead with users.
I always wondered what was on the drawing table for Fostex right before ADAT and digital kicked in...were they going to introduce something in a large format tape deck, or...???