He lost to Krammnik in the World Title Match. Deal with it.
While it is true that Kramnik holds a title of World Champion, having defeated Garry in a title match, it is not the FIDE title (which is held by Ruslan Ponomariov of the Ukraine).
So because it's not FIDE, your assertion is that somehow it's not legitimate? Kasparov was the best player in the world, was beaten by Krammnik, and will have to beat Krammnik to regain that distinction.
Furthermore, Garry has a plus score against Kramnik in the overall match of all games played.
Krammnik was in his late teens when he lost many of those matches, and Krasparov was in his prime. Times have changed.
In fact, he recently defeated Kramnik in a match (the Botvinnik Memorial).
Until he does it with the World Championship on the line, it doesn't mean squat. Kasparov is tired; his day is done.