I don't recommend them, except for research purposes. Now I'm in the hole for 2 of them and feel obligated to see the third. Thanks, Joel and Dane!
By cynical, I'm referring to a specific tone that permeates the movies. It tears apart any sense of idealism you could have about the films. In them Optimus Prime is a 'hands on hips' super-speech giving demagogue, who preaches about peace and bravery and doing the right thing, but he also ruthlessly rips the faces off of opponents who have already been defeated, or pose no threat in the first place. The main character is a boy who you think would be happy, or wowed by 1) discovering friendly alien life or 2) becoming instant best friends with a transforming super robot, who is also an awesome car, but, to the contrary, he's mostly really annoyed by it.
The whole tone of the movies is negative, it seems like everyone onscreen is always arguing about something. Nobody trusts anybody else and something seems to always, ALWAYS be getting humped.
To me, this seems to be a reacting against what you'd expect to find in summer family blockbuster fare.