Both movies were great. There Will Be Blood was a lot better though IMO. Great acting, really good dialog , amazing cinematography, and a great chemistry between the two opposing actors (Day-Lewis and Paul Dano.)
90% of moviegoers these days just want to go and watch CGI crapfests like 300 or Transformers. All visuals and no substance. I mean they are cool for what they are (well 300 sucked, Transformers was okay to an extent) but they lack anything worth thinking about once the movie has ended.
If you didn't find either of those movies entertaining you probably fall into the CGI crowd.