There's nothing stopping a sequel from being good (Aliens, T2 and etc) other than the makers putting out crap.  For every Aliens there's 50 AvPs, unfortunately.  I was mildly hopeful for The Predator, but I'm not tremendously surprised it's not stellar.
but....
What about special effects and current year and stuff?
I quite liked the prequel they made of The Thing for those reason-ish reasons.
Effects cannot improve a garbage script or acting.
Wiley.