Opera singers sing full-length roles in classical operas, in houses which seat thousands, and without the benefit of a microphone can be clearly heard in the back row of the uppermost balcony / gallery seats. They sing full-length recitals, in a similar venue, of unabridged classical repertoire.
Sarah Brightman has never done these things, and, being smart, never will, because if she did that work in those contexts, she would show as reallllly bad and plainly out of her league.
Brightman, Josh Grobin, Andrea Bocelli, Katherine Jenkins, and the similar likes of -- are all "Popera" singers. They've never sung an opera or an (oratorio) -- at least not without benefit of microphone -- in their entire lives.
http://www.independent.co.uk/arts-entertainment/classical/news/these-people-have-never-sung-an-opera-in-their-lives-6296320.html
So, I do not care for her voice, far thinner and less in tune than many a singer of oratorio, lieder and opera.
You might find you love the voice and musicianship of Elly Ameling...
Here she is singing Schubert's amazing " "Nacht und Träume"
http://www.youtube.com/watch?v=2TnK7tPTwHE
Ms. Ameling is still known and loved for Schubert, Mozart, Bach, etc. If you can find it, one of the finest performances of Bach's 'Wedding Cantata' - was with Ms. Ameling singing the soprano (with the additional attraction that was on period instruments and an overall fine performance:-).
From the Wedding Cantata, here is the aria, "Weichet nur, betrübte Schatten" as sung by Emma Kirkby,
http://www.youtube.com/watch?v=FRyoE1F0Fw4
But for me, Ms. Brightman??? Well, just listen to those links above :-)
Best regards.