It's difficult to review a movie like this, but it obviously is doing exactly what it wants to do, and can't be called anything but a success. The people this movie is made for will love it, what anyone else thinks is besides the point.
But here goes.
The movie is an extended skit more than anything else. Over the top action with a cast of characters who are almost like a mosaic of popular culture icons. Kung fu master, dinosaur/cop-hybrid, Norse viking gods, Hitler, laser raptors, arcade cabinet robot, etc. The movie's aesthetics is that of a well used VHS, matching the 80s vibe of the plot perfectly. There are jokes and gags throughout, some which are delivered with a 100% confidence, and others (for some reason) delivered ironically.
In addition to a skit, this is also very much an SFX-reel, where David Sandberg and his people show off what they can do visually. No concept seems to far fetched for them, and they're not concerned with photo realism - they will gladly avoid it if it makes for a funnier/crazier scene. It's fun to see how they mash up computer graphics, practical effects, green screened actors in costumes and stock footage. It makes you wonder why more young people are not out there making movies. Hopefully this will inspire them.
Despite being what it is, there are flaws. As mentioned before, some jokes are delivered tongue in cheek or ironically, which takes away from the fun of the film. As I see it, they are not trying to poke fun at 80s/90s action movies, but celebrate them. The audience is aware over how cheesy some of the lines are, no need to point it out. I guess the cast works, but it seems to be a combination of perfect matches (Thor, the viking girls) and people being friends of the production crew. For a movie with this, bad acting is not a problem. But it's more enjoyable with exaggerated performances (see: Thor) than "doing this for fun"-ones (like many of the smaller parts).
Now, I know this review will not change anyone's mind. If you like the concept, watch this movie at once and love it. If you hate the concept, or feel it's not for you: you're probably right. I'm giving it a 7/10 because I mostly enjoyed it. I hope this is the start of an interesting career for David Sandberg.