Yes, he was definitely responsible for his own actions!
I did feel a little bit sorry for him at the beginning, because he was treated differently because of his looks. Basil Hallward worshipped him, and made him feel like a god. Lord Henry treated him like an experiment and didn't really care about him. He loved Sibyl Vane, but his own devotion to her destroyed her ability to act, ultimately ruining the love and ending her life. In these situations he seems confused and naive.
After this, however, he decided not to care about Sibyl's death and he realised that beauty, youth and indifference meant he could live selfishly. In this part of the book I did not feel sorry for him!