ROTF is big, is loud, is long... all the symptoms of sequel-itis. Transformers was a total thrill-fest, so the only way to up the ante is to add generous helpings of more. More military hardware, more combustion, more backstory, more locations, more cheesy romance (ok, maybe I'm jealous 'cos it's Megan Fox in question), more OTT laughs, and more characters than an F-16's threatboard could possibly keep track of.
So ROTF didn't get many good reviews. It's probably the law of diminishing returns at work. The first time may have been highly satisfactory but the second, with all the additional trimmings, is a bit too much.
One feature the critics can't seem to get over is how much running, ducking and covering our protagonists, Sam and Mikaela, have to do. Not very heroic, the critics seem to say. I think they've forgotten how their own game of (American) football, on which both Transformers movies are based, is played. Sam has the ball, everyone runs interference for him, clearing the path so that he can score the touchdown. Perhaps Sam is the new breed of action hero -- the running forward rather than the quarterback? Let's see if this archetype repeats itself in other action movies to come.
I went in for the Transformers Movie Marathon, so I watched both movies back-to-back. I noticed that a second viewing of Transformers allowed me to see things I hadn't seen before the first time, and I guess it'll be the same for ROTF as well. There's so much sensory input, it takes time for the mind to process it all. If anything, that's the main problem with ROTF. Leave brain at door, settle down confortably with free-flow popcorn and Coke, be shocked and awed by the systematic demolition of civilization, have fun! Why make things more complicated than that?