Let's start with the villian. Nero's backstory, his vendetta and means of execution were all strangely similar to Shinzon's from the last film. It's almost... and I can't even believe I'm saying this, but it almost felt like they were paying homage to Star Trek: Nemesis. Sure, the villian in an action film is only really there to die to the hero... but Nero, the terrorist Romulans, the ridiculous ship--it wasn't just lazy, it was recycled. I was sitting in the theatre in disbelief. The Enterprise has saved the day from stronger adversaries on numerous occasions. And I didn't have to pay $10.25 to see it any of those times.
I'd just like to point out, Shinzons whole gripe was the fact that he was the "shadow" of Picard, he didnt want to be the afterthought in history, he wanted to be remembered as the better, stronger person who had no problem with slaughtering billions of people if it had to be done.
Nero on the other hand is driven by revenge, revenge for the death of his wife and his unborn child. While Shinzon calculated his way to the top of Romulan government, after the destruction of Romulus, Nero found and escorted the high council to a Romulan outpost, where they were experimenting with reverse engineering borg Technology, The only ship there was Nero's minig vessel, so they retrofitted it and let him on his way for vengence. After Spock stopped the Hobus Supernova, Nero and Spock were sucked in to the resulting Black Hole. Nero was thrown a 150 years into the past, and bided his time for vengence against Spock (Who had promised to help nero save Romulus, but failed).
Nero is just driven mad by Anger. Shinzon was driven by Power. Similar, but still different Character motivations.