Nadal has lost three times in 2013, and won maybe 55. Federer is about 34 and 10. Djokovic has only lost 8 times, and Murray's stats would look quite similarly impressive (9 losses against many more victories). Ferrer is 42 and 14. James Blake, number 100 in the world, who has just retired, has a career record of 61 and 42 in Grand Slams. He was an extremely good player at one point, and retires with a very respectable record, but way below the level of those who win repeated tournaments over the course of several years.
In part because of his extreme dominance on clay, Nadal has a career winning record against Murray, Federer, Roddick, and Novak, and probably against every other player he's played at least 3 times. He is 21 and 5 against Ferrer, an excellent, excellent player who's ranked number 4 in the world, and 16 and 3 against Berdych, who is #5. He has won 15 straight times against the Czech. If Federer is the greatest of all time, Nadal can say he has a winning record against the best player ever. So what does that make him? He has a 6/1 ratio of wins to loss in his career. Federer has won more than 900 professional tennis matches and lost only around 200!
In baseball, most teams in the major leagues are between .400 and .600 in winning percentage, so the typical mismatch is between a team that wins 9 out of 20 and one that wins 11. (The highest percentage as of today .606. Two teams are below .400.)
The difference is that the top tennis players are playing against the equivalent of minor league players, a lot of the time. The game is structured differently, so you don't get to even play another match if you lose the first round of a tournament. A .500 record means you lose and win about half the time in the first round. Or lose a lot in the first round and go into deeper rounds once in a while. What is truly amazing is a player at the top of his game who is virtually unbeatable, even by another stellar player. A pitcher never wins 20 or 30 games in a row.
Baseball is subject to numerous chance factors, so that a team that is objectively better will lose to worse teams on any given day. The season is long with many games, and every team plays the exact number of games. There ought to be a technical term for sports that are more subject to chance factors, like golf, soccer, or baseball, vs. sports in which the winner is much more often the better team or player, like football or tennis. When I see two pro tennis players who aren't in the top 10 against each other, I think either of them could win on any given day. Say the number 35 against the number 25 in the world. So in that context tennis seems much more "noisy." A top player who isn't having a horrible day can almost always put away even a superb player.