We have the same issue here, and have for awhile. DD's (3.1) pretend and interactive play is light years ahead of her agemates. I typiclly end up being her only play friend....although, at the suggestion of our librarian when DD was 2.5 we moved her to the 4-5 year old storytime group, and she has made several good friends who she now gets to playwith outside of library time. She has even developed one "best" friend, and now in storytime they actually get in trouble for giggleing and talking and they have to sit together always.
So DD definitly prefers to play with me,when older kids are not avialable...now if she can fnd friends who are 5,6, and 7, she has a ball and enjoys herself and they enjoy her. Infact on of her good friends is a 7 year old, and she plays with him and looks forward to his school breaks so they can spend time together. I don't have any ideas for encouraging indeppendent play really...it has gotten a bit better lately, but I have been more firm when saying I am busy and not stopping what I am doing. This was really hard for me at first but has helped. Good luck.
