Metacritic is a fun site to use and it's entertaining to see what kind of scores certain games got. However, I do not try to use metacritic as a way to measure the actual quality of a game. A whole lot of ports get lower scores than the original, especially if nothing changed. In an unbiased review, both would receive the same score. Reason? It's the same game, you can't say the quality of a port is lower because it's the same. I even see ports that get nothing but slight improvements and the score still is lower. This expectation is also what ruins the scores.
It's not like when they port a game that they're trying to sell you a new IP. You should be expecting the exact same game. Not MORE. Giving more is a bonus that should RAISE the score (unless the bonus detracts from the overall game itself).
