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.
Kasparov is the highest rated player. Deal with it.
So because it's not FIDE, your assertion is that somehow it's not legitimate?
Don't take my work for it, go ask FIDE and Ruslan Ponomariov.
Krammnik was in his late teens when he lost many of those matches, and Krasparov was in his prime.
OK, following your logic, Kramnik is the one now in his prime and Kasparov is not. Therefore, Kramnik should now be dominating Kasparov, but he is not-- neither in terms of rating (which is a measure of playing strength) nor in terms of games against Garry.
Whatever. Hopefully we will see a re-unification match (which all three parties, Ponomariov, Kramnik and Kasparov have already committed to) and the question of who is the real world champion will be decided.