Hi John,
Zombie movies do not get more than a blink from me. I have no interest in that kind of horror movie.
It does take a premium sci-fi to have me give it any flattery. I grade them into categories. Such as awesome special effects (Avatar) and interest and credibility (Contact).
Zombies, no way.
One particular movie that I disliked is Space Cowboys. It just had so many errors in it that it lost credibility. That is possibly the one major issue that I have regarding sci-fi. The large numbers of errors and their magnitude.
Cheers