Well, the character of Michael Sullivan could have become interesting if he had been developed during an arc of several episodes by becoming totally sentient as the Doctor (he would have navigated between the 24th century of Janeway and the end of the 19th of Fair Haven) OR even, in showing Janeway meeting by accident, a totally human Michael Sullivan. So, what she refused to live with a hologram who pops on and off in, she made it with a being made by flesh and by bone.
It's certainly the reason why her loving "adventure" with Sullivan was never taken seriously contrary to her adventure with Jaffen.
(I like Fair Haven & Michael Sullivan but well, it was above all a joke. Again, more development would have been welcome).
Seriously, when I see Janeway/Sullivan, I don't get those who are hooked with Seven, a human being at 100% becoming Borg, and the Doctor, who is a hologram at 100%, as a potential romantic couple.
I mean, I find the idea of a romantic relationship between people from different races, WONDERFUL but come on, how is it possible to get the same thing between a living being and a hologram, which by definition, is an image thrown in 3D, even if it is sentient (able to move easily from a space to another on). For me, Janeway/Sullivan = Seven/The Doctor.
Alright, I know that the ridiculous doesn't kill anymore but all the same, it's very odd and even disturbing! In the same time, it's Star Trek: Voyager which collects -maybe not all the possible and inconceivable- implausibilities but hey, the serie offered a lot to us, so... !