What he predicted was 'de Gloria Olivae' - which can be loosely related to the Benedictine Order, as one of their symbols is the olive branch (Benedictine monks have been raising olives for nearly a millenium). However, Pope Benedict is not a Benedictine, it would seem. Does St. Malachi score a near-hit for this one? Very hard to say, I'd say.
Other than this rather convoluted connection, there isn't much chance that St. Malachi predicted Pope Benedict after all.
On the other hand, we must always be mindful that Pope Benny may well have been familiar with St. Malachi's prophecies, and may have chosen this name as a result; if this is a true tendancy - which it could well be - then what we have is a potentially self-fulfilling prophecy. It should be interesting to see if the next pope finally goes by Peter, a name never taken by Popes. Further, if there are any Popes after him at all.
From what I've read of St. Malachi and his 'prophecy', there has been a LOT of stretching to fit prophecy to pope over the years. Nevertheless, there is a feel of synchronicity to some of his predictions - like the Middle Moon pope, etc.