It's a fine distinction. If the reviewer says the game IS unfinished, then he's stating something as fact, which he should not do unless he can back it up. If he can quote the project leader saying something like, "Management mandated unreasonable deadlines that forced us to ship before we had time to do proper QA," then it's safe to call the game unfinished. If he can't back it up, then the reviewer should not say a game is unfinished.
But if he says the game FEELS unfinished then that's perfectly OK. "Feels unfinished" is subjective; it connotes exactly what j_factor said: the game seems like it needed more testing or seems like it is lacking features. Maybe it's not; maybe it was playtested to death and it has every feature the developers wanted, but it doesn't
seem that way in the reviewer's opinion.
Calling a game "rushed" isn't quite the same. No software developer has EVER been involved in a project where they weren't being rushed by somebody.
So it's reasonably true to say
every game was rushed. I suspect that when most reviewers call a game "rushed," they're referring to how it
feels, not what it
is. It feels slipshod, it feels buggy, etc. -- the kinds of things a reviewer is supposed to say. But if the reviewer is saying, "This game was rushed to market and therefore DID NOT ship according to spec," that's a factual claim that has to be supported somehow.
A lot of it depends on the wording of the review. If the reviewer seems to be making a factual claim when he's really stating an opinion, or if it's not clear what he means at all, then it's a bad review.