It certainly isn't an appalling film (otherwise I would never have given it a 6 - and I verged on giving it a 7), it just didn't get the balance right this time around. It was far too light-hearted for starters. I loved the humour that first one possessed and I did in this one too, however it just took up too much of the runtime. If people asked me to choose one genre that this film was I would probably have to say comedy. I should be saying horror.
Secondly, the film was so intent on being clever (and being a homage to 'Back to the Future') that it completely forgot to have an interesting plot piece at the centre of the film. The killer angle was almost like an after-thought this time around. Whereas in the original it drove the film and everything else fed off that.
The first film was so good that I didn't want anything to change and taint what was created in that film. I left the cinema this time with a bit of a bad taste in my mouth. If a sequel absolutely had to be made I would've preferred completely fresh characters (even though I love the ones that are in these two films) and for them to just do a seperate story. Maybe that wouldn't have worked either (speaking further to my point that a sequel simply wasn't needed) but at least it would have left the original intact. I hear a third addition to the series is on the way. Hopefully they get it right (whatever that means) next time around.