Transformers: Revenge of the Fallen (Transformers 2) is not what one would refer to as a good movie in the sense that Forrest Gump or Seven Samurai might be considered good. Transformers 2 is, however, an awesome movie in the sense that summer blockbusters are designed to be awesome. It's pretty typical to see a movie that's got crazy effects and action but with a story/plot that mostly exists to give pause and glue to hold things together, which is somewhat farcical, in my opinion.
The logical conclusion to the trend of summer blockbusters is that story/plot isn't actually that important and, if done wrong, can really drag a movie down. So, what happens if you reach that logical conclusion and make a movie that is an open acknowledgment of the frivolity of plot in summer blockbusters? You end up with something that is a gorgeous, shiny, moving piece of art, that pleases your senses but not your intellectualism; you end up with something that every traditional movie-watcher will think is terrible as they hunt for plot and a, so to speak, good movie.
This is the case for Transformers 2. Critics, in looking for plot and traditional quality, have failed to see the gorgeous, shiny, sense-satiating, monster of an experience that Transformers 2 is. The critics made a similar experience with Speed Racer, which was not very compelling but nonetheless excessively beautiful.
In addition to the amazing experience that Transformers 2 is, its quality has also inspired, what is probably the finest review of anything, ever. io9 puts it quite well in their review, Michael Bay Finally Made An Art Movie, which I completely agree with. Excerpt below:
Transformers: ROTF has mostly gotten pretty hideous reviews, but that's because people don't understand that this isn't a movie, in the conventional sense. It's an assault on the senses, a barrage of crazy imagery. Imagine that you went back in time to the late 1960s and found Terry Gilliam, fresh from doing his weird low-fi collage/animations for Monty Python. You proceeded to inject Gilliam with so many steroids his penis shrank to the size of a hair follicle, and you smushed a dozen tabs of LSD under his tongue. And then you gave him the GDP of a few sub-Saharan countries. Gilliam might have made a movie not unlike this one.
In short, read this review; ignore the other reviews; go see Transformers 2; get overstimulated; and enjoy the culmination of all that is the summer blockbuster.