Besides which...who's to say Romulus isn't destroyed in STO? If you've been keeping up with their projected history, there are technically 2 Romulan Empires. Of course, STO says that the Klingons go to war against the Federation...under MARTOK. I call bull. STO is gonna be crap, especially when they decide to "hot rod" a Sovvie to be their flagship and apparently the Klingons dug up a 22nd century ship as their new primary ship. Sorry, STO gets two big thumbs down as far as story.
And remember guys, both Nero and Soran have the Khan-like madness going against what should be logic here. But Nero lost his home, his family, and probably a good deal of his friends.
As for his vendetta, it likely starts with Vulcan because of Spock's involvement. Whether it's Spock's action or inaction, or perhaps Vulcan/Starfleet's lack of action, that results in Romulus's destruction, either way Nero would have a clear reason to go after Spock's home. I think someone on TrekMovie.com put it best though: "Romulus goes BOOM?!? Talk about taking things personally - this guy makes Soran look like a Red Cross worker."