is Bobby Fischer better than Garry Kasparov?

They never played each other directly, so it's a hard question. It depends if you're asking 'if you resurrected Bobby Fischer of 1972 and Garry Kasparov of 1999 (the peaks of each player), who would win' or 'if you trained each player from scratch using present day training methods, who would win'. The answer to the first question is probably Kasparov, since he had a slightly higher peak ELO and chess theory and understanding advanced between 1972 and 1999. The answer to the second is anyone's guess, but I would say Fischer because his obsessive nature would make him work very hard. Also, Kasparov went to Botvinnik's chess school at age 10, while Fischer had no formal training at this age, so this gives Kasparov an unfair boost.

Yes, Kasparov had unfaiir boost going to chess school and every player in history who had a coach must return their titles and prize money (dig that bastahds out of their graves)

Erm, that's not what I said

Bobby Fischer never won a single game, while champion. And never successfully defended his title.