I don't know what I was expecting Arthur to be. I never saw the original movie, had never seen Russell Brand in anything and only went to see it because Lauren wanted to see it. I don't like romantic comedies and I don't like Katie Perry (which doesn't have anything to do with Arthur, it's just that the only thing I knew going into the movie is that Russell Brand is married to her in real life).
Plotwise, Arthur was pretty predictable.
But that doesn't matter 'cause I really enjoyed it anyway, much more than I expected to. And I think that was entirely because of Russell Brand, who was far more charming and funny than I was expecting. He has great delivery; the best lines in the movie, that I think other actors might have really tried to punch, he sort of threw away, said them casually as if that's just how people talk. And it really worked.
Helen Mirren was good, Luis Guzman was good, I couldn't decide if the woman who played Naomi reminded me of Zooey Deschanel or Chloe Sevigny, and it was nice to finally see a movie that acknowledges how unpleasant Jennifer Garner is. I can't stand her (ever since she snottily told Conan O'Brien "Snuck isn't a word, Conan, and you went to Harvard and you should know that." What a bitch! ... Of course, then Conan brought out a dictionary and read her the definition of snuck, ("past or past part of sneak") which just makes me love him more).
My favorite part of Arthur, though, is that it made Frog And Toad a major plot point.
And if you aren't familiar with Frog And Toad, that's your problem.
End of line.