The graphics of M&M IX were outdated when it came out. (as in every other M&M game, btw.)
Those that remember that fact will probably be automatically biased, whereas those that don't may be able to look past that (and enjoy the game if there are other things to like).
EDIT: Oh, that's right, M&M IX is already here. Most of the bugs were fixed, but most of the reviews are calling it "meh".