It is based on the very first draft of the first film, and finds itself deciding against everyone of the few redeeming qualities about the first film. For starters, while Kevin Bacon's character wasn't exactly brilliant in-terms of portrayal, there was a certain amount of wit and depth to the character in-comparison to what we usually see in horror movies. Unlike the first film, Hollow Man 2 starts out as a nonsensical horror-film and never really pokes its head out from the hole.
The characters come across without much in the way of flushing out, a detective and a female scientist with oh-so precious information about something or another. Meanwhile, the military is trying to them and a mysterious ghostlike man wandering around wreaking havoc.
The characters feel cookie-cutter and their acting doesn't have a lot of heart in it.
All of this is certainly be expected when you consider that the movie had a decreased budget, but it is still saddening to see. The special-effects and neat looking transformations done by the invisible man have been completely discarded. It isn't even the idea that the special-effects are terrible, because that could be worked around through wit and creativity.
There has certainly been other "invisible man" films that have done more with less, but this movie manages to do remarkably less than what the original film did. There is no fun to be had, and it just seems like a bad horror film with invisibility serving as nothing more than a minor wrinkle in the fabric.
In conclusion, not only does Hollow Man 2 fail at fixing some of the problems that were had about the first film, it actually takes all of the redeeming qualities that made it interesting in the first place. It's a common-practice in sequels to take what was loved about the original and inflate it. Hollow Man 2 seems to take everything that I hated about it and magnified it a few times over.