What attracted settlers to the Middle Colonies?

The land, the chance for a new life, abundant resources, etc.

Think about it, with England being so powerful, they needed a lot of resources. Of course those resources are going to diminish every so often, so this is just one reason that the settlers moved there.

Another reason is business and profit. Think about this as well; Where were the middle colonies located? Near the sea of course. This was very beneficial for merchants and shipbuilders and the like.

The land was very fertile, practically virgin land except to whatever Native Americans had been there at all, if any.

Many traditions began here, and some were simply brought over. All in all, there were many good reasons as to why settlers came to America. :)