Disneyland Paris is certainly a notch (or two) below all other Disneyland parks. It looks like Disneyland with similar characters and impeccable theming. However, the current owners don't hold cast members to the same standards of friendliness nor is the park as clean.
Disneyland Paris has the best versions of Big Thunder Mountain and Haunted Mansion (Phantom Manor) and an interactive castle, but overall there are not as many rides in the park as in its American counterparts.
Families and Disney fans will still have a wonderful day, but just not as "magical."