I come to you with a question. After Federer won his 15 grand slam title he has the record for most grand slam titles for a single man. He has done this over a short span of seven years. He has clearly been the most dominant in his sport. But has he been more dominant in his sport than Kasparov was in chess? Kasparov was World Champion for 15 years and set the record for highest peak rating reached and holds the record for most consecutive weeks rated atop the rating list. Both men have  dominated their sport, but who was more dominant? I could have used Paul Morphy instead of Kasparov, but i chose not to, because Morphy had no one at his leve. Kasparov had Karpov and Federer has Nadal.