The riff for Episode II felt sub-par, mainly because it seemed like the whole movie consisted of making fun of the fantasy names (its "Naboo," we get it) and making pooping sounds whenever it showed someone sitting in a chair (once you hear it more than twice you realize why you got over poop jokes in the 5th grade... okay, 7th).
More than that, Chad Vader should have had more lines. I don't know how Guest Riffers work, whether or not lines are written for them or they submit their own material (and therefore Chad simply didn't have much to offer), but it seemed like he had only two jokes, three tops.
Honestly, there were only two parts I really laughed out loud at, and one of them was in the Rifftrax preview: the part where the landing craft explodes and Mike says, "Glad we didn't take the local!", and when Dooku walks up in the arena during the Jedi/Geonotian and "says," And now, a reading from St. Paul to- what the hell?!"