Um, I don't read series romance (i.e. Harlequin or Silhouette), I've never read a Mills & Boon. I do read a ton of historical romance and paranormal romance. I don't particularly fancy either Nora Roberts or Judith McNaught.

Anyway, some romance favorites of mine:

Paranormal in a futuristic setting:
Nalini Singh Changeling/Psy series

Paranormal with humor in the mix:
Kresley Cole Immortals after Dark series

Sci-fi/Futuristic:
Robin D. Owens Heart series
Lora Leigh's Breeds (this one is very spicy, so if you don't particular fancy explicit, skip this)

Time travel:
Lynn Kurland
Karen Marie Moning

Paranormal with elements of romantic suspense:
Lynn Viehl

Romantic suspense:
Linda Howard

Erotic Romantic Suspense:
Lisa Marie Rice