I thought this movie was amazing. Sure, the characters were all very flat and one-note and archetypal, but that's kind of the whole point, that's what Del Toro was going for. I didn't care for the main character (Raleigh) very much, but I thought the rest of them were wonderfully done. I disagree about the plot, I thought the storytelling and pacing was excellent, nothing felt rushed or shoehorned or slow or disjointed at all and it all flowed extremely well. I loved the action scenes, I didn't think they felt video gamey at all. And yeah, it was predictable, and yeah, again, that was kind of the entire point. That's like complaining that Avengers was predictable. Not every movie needs twists and turns, films can be good for other reasons too.
I don't know what people are complaining about. When I went into this movie, I expected a love letter to the giant robot/giant monster fighting genre, and I expected it to be fun and goofy because that's what this genre has always been. I got exactly what I expected, and it was beautiful. I couldn't recommend this film more.
Also, my hope is that the success of Pacific Rim might lead to Del Toro's take on At The Mountains Of Madness actually being made. Because that would be a dream come true for me.