That certainly is a matter of conjecture and debate; however here are a few thoughts. Garry Kasparov is widely considered as the best Chess champion because he is probably the strongest player. Emanuel Lasker held the chess champion title for 27 years, longer than any other person; however, he did not have very many challenges. Alexander Alekhine held the title for 17 years and is thought to be the strongest player of his day. Kasparov chose him as the player to study from most. Paul Morphy was never the chess champion on a formal basis since at his time there was none. Informally he was acknowledged to be the best player in his time and some chess greats refused to play him. Bobby Fischer chose him as the player to study from the most. To be sure, there are many others who deserve consideration in this answer, but this enough for now.
Chess World Champion
The current chess champion is Viswanathan Anand.
The current world chess champion is Viswanathan Anand
Bobby Fischer is not the current World Chess Champion. Anand is.
The first American World Chess Champion was Robert Fisher.
TRUEBobby Fischer became world chess champion in 1972.
The "Lion of madras" Viswanathan Anand of India is the current World Chess Champion .
Viswanathan Anand is the current World Chess Champion as well as an Indian Grand Chess-master .
kasparove of course! he has the highest rating
Bobby Fischer became the first American World Chess champion in 1975.
Chess World Champion Viswanathan Anand is rated 2780 on the March 2013 FIDE rating list.
The brilliant Paul Morphy was both. He was recognized as the world chess champion but before there was a formal champion.