I really couldn't say which I would say is the worst. We really haven't seen a lot of the ones I've seen listed here. We all liked HSM (my husband and I haven't seen 2 or 3, but the girls have), Camp Rock was merely OK (but we ALL agree that the Jo-Bros were the definite low-points), and my husband and I enjoyed "My Date With the President's Daughter" and "Zenon" long before the girls were born.
However, to me, the pinnacle, and easily the #1 favorite among all 4 of us, is "Lemonade Mouth"! It's so good that sometimes my husband and I will watch it even if the girls aren't home or are asleep! Just yesterday the girls wanted to watch it again, and it was an easy "yes". It's just a fun movie.