But it only works because it is so strictly regulated, and run just for the Japanease manufactuers. The cars are not GTs anymore but prortotypes.
In FIA/ALMS GT there is more variety, plus stable, long term regs that work, due to GT1 no longer being involved.
Although the JGTC is great, it is a 3 marque only series in GT500, and will be so for the forseable future.
I think FIA GT now has competition at least as good as JGTC, plus those V12 Ferrari and Jaguar engines.