I never liked PHANTOM OF THE PARADISE much either. I don't hate it, and I wouldn't mind seeing it again to see if my opinion has changed. A friend loaned me the laserdisc in the 1990s. That's the last time I watched it.
Yes, THE PHANTOM OF THE OPERA looks very nice on Blu-ray. When I first got my player, I did an A/B comparison with the DVD using the "Masquerade" number as a comparison, and I was astonished at how the DVD, which I thought looked good, was really soft and a bit hazy compared to the sharpness and clarity of the Blu-ray.
I don't find the singing very compelling in the PHANTOM film. Butler and Rossum can carry a tune, but the singing is just there. There isn't much to support it (she's really wan as an expressive singer; she could NEVER have been a prima dona in an opera house with that small voice).