My first daughter didn't sleep through the night on her own until she was 3 or so. Our problem included the lack of a consistant routine. She also had some food allergy issues that made her uncomfortable but once we put a bedtime routine and a consistant bed time in place things got a lot better. I used to let her fall asleep to a DVD, but once we stopped that and read to her or told her stories in the dark she slept much better. We had to teach her how to be okay alone in her bed and how to soothe herself to sleep. Once she was okay initially falling alseep without the TV or me then I think she wasn't so scared when she woke up in the middle of the night and instead was able to go back to sleep.
Believe me, this whole thing was exhausting and time consuming. It took months to teach her to sleep after the 3 years of just doing whatever worked in the moment. But, for the last 9 years she has been a great sleeper with no bedtime struggles at all and that has been very worth it.
Good luck to you. Take care,