Hey, I've got nothing against horror 'B-movies' - in fact, they make up a significant proportion of my DVD collection. You don't have to have major actors, great special effects, or even a particularly original story to make a movie enjoyable - as long as it entertains then it usually fits the bill. However...
If you make a film with the word 'monster' in the title, it does tend to set an audience's expectations. If you sat down to watch 'Snakes on a Plane' you'd probably not be expecting Shakespeare, but you'd be looking for something that's just a bit of harmless fun. If you got one sickly-looking adder ten minutes before then end, then you might feel just a little bit 'short-changed' from what the title promised.
'Monster Portal' is an adaptation of an HP Lovecraft story, which is fair enough, but it does relay on giant creatures as part of its central theme. Sadly, the movie doesn't have the budget to really pull it off. Yes, there are a couple of monsters sprinkled here and there, but not only is it not enough to justify the title, but they're rendered about as well as your average Playstation 2 cut scene.
Now, I'm happy enough to ignore the special effects if the story is overall engaging and fun (or in a horror movie's case 'scary' would suffice), but here the acting is bad. Yes, I've seen enough horror movies to know I'm never going to get 'Oscar-worthy' performances, but in this case it basically feels like the actors are reading their lines off a cue card which is just out of shot. I guess I shouldn't really put all the blame on the actors, this script is pretty basic and they're probably doing their best with the awfully generic lines they're given, plus you'd think the director might be able to coax something out of one or two of them.
It's not the main characters who are the (total) problem. They don't turn in very good performances, but I can just about excuse them. It's more the secondary cast-members who might as well be your average passers by who were roped in to read a line or two here and there.
As I say, B-movies can be fun, but this one just tries to bite off way more than it's capable of. With a higher budget, better actors and script it might have worked, but, ultimately, it couldn't make anything of its lofty goals.
