These days when a sequel comes out to a popular game, you can expect change to try and get new fans. Titles like Dragon Age II change up the gameplay so much that fans of the original no longer enjoy it. Game sequels used to have the same basic mechanics with a new story and more content. They were made for the existing fans. Today, Portal 2 sticks with the old formula, keeps the great gameplay of Portal, and adds enough new content to make it a sequel worth buying.
Portal 2 was so awesome— Valve got it right. It’s a shame more developers don’t think like this.