The funny thing about the whole "Ayumi is a over the top diva and Hikki is a girl next door" thing is that while Ayu was born poor and had to fight her way to stardom, Hikki was a rich kid whose parents always had conections in the industry.
Not to say one deserve it more than the other (as I myself always liked Hikki more as a musician), but Hikki really had it far easier when becoming a popstar. Not that this by itself would give her the sales she got and still get, but it's easy to understand why she feel she can release music when she feels like it, unlike Ayu who sees her career as a, well, career.
About Gackt and Hikki's lastest releases being stronger releases than MIJ, that happens when you take your time to release your stuff and doesn't need (or feel you need, we don't know) to release a new album every year. Gackt and Hikki could get their times into crafting the sound they felt like, while Ayu depends entirely on having the right inspiration to release an amazing album. I really liked MIJ, but I don't think it's one of her best. Still didn't give Fantome a proper listen.
Both Hikki and Ayu have a tight control over what they let the public see or not see about their private lifes, and both of them are +- private about what they do. For some reason people get bothered because Ayu is phographed with her significant others, even if the only thing we know about them is that they are together, without any other detail or insight about their private lifes. I disagree we know Hikki's views on LGBT issues because the was asked about it, during her american tour she threw those signed balls at the audience and the balls had pro-gay marriage messages on them. Her personal blog (does it still exist?) also gave a lot of insight over her world view and even let we know she had the hots for Rafael Nadal.
Unless she got really better at acting I don't think that was fake at all. Usually her fake crying doesn't affect her voice, you see the tears but she keeps singing with she same quality (or lack of) she already had through the song, while her voice really goes to hell when she gets emotional for real.
She always did that, even during her peak, and so does Hikki. The difference here is that Hikki has 8 albums released through 18 years while Ayumi has twice the albums released over the same time spam. It's no surprise people feel like the constant shift of direction from Hikki comes from inspiration while Ayu's come from desperation, but they are pretty much doing things the way they always did.
Still believe Ayu would benefit wonders of having a hiatus...