This is a sequel?

I guess yes according to Wikipedia: http://en.wikipedia.org/wiki/Sequel

"A sequel is a work of fiction in literature, film, and other creative works that is produced after a completed work, and is set in the same "universe" but at a later time. It usually continues elements of the original story, often with the same characters and settings, although this is not always the case. For example, if the main character dies at the end of the first work, a new character (such as a son or daughter) may take up the role in the sequel. A sequel is somewhat different from a series, in which the same character appears in a number of stories, although some media franchises have enough sequels to begin to resemble a series."

Interesting discussion at this link regarding other definitions (prequel, sidequel, etc...)

So yes this is a sequel but according to this term you can't call Hollowman a "series" of movies. It's obviously a gimmick and very annoying if they only loosely tie the sequel with the original characters.