It's Johansson and Gaudio for sure.
Gaudio's a *pretty* good player; but who would really argue that peak Coria, Ferrero, Nadal, Kuerten, Muster, Bruguera, and Courier weren't better and more feared on clay? In other words, at one point, all of these guys were so confident and playing so well that they were class of the field level on clay; but Gaudio's one of those guys who's the class of the bridesmaids, never the bride. To me, Coria GIFTED him a French Open title on a silver platter his nerve induced cramps were so bad...and Gaudio STILL barely, and I do mean, barely, won it.
Johannson to me, well, he's actually more talented than he gets credit for; but he's really NOT what anyone's ever considered an ELITE level talent. Sure, if he gets hot here and there, he's dangerous; but that's ALL. He got a decimated draw that year and Safin came out flat, but Safin also had to face a truly treacherous draw unlike Johansson to get to the finals. Put it this way. Who's better, peak Safin or peak Johansson? Exactly. The difference to me between fluke slam winners and the real deals are that the non-fluke ones, at their peak level; they are darn near unbeatable, Johnasson isn't that guy...that's like saying if Alberto Berasategui or Alberto Costa had won a French because their more elite opponents came out flat. In Costa's case, he actually did win that way so it does happen. Though to be honest, he deserved it more than Johansson did in my opinion; because he had a tougher path to glory that tournament than Johansson did and no one can take that away from him. He battled HARD that tournament and played at the highest level I've ever seen from him. To be honest, when Johansson won the Australian Open; I did not get the feeling like hey, this is the absolute best this guy can play, he's playing above his head and is in the zone. Instead, I saw a guy who got a draw that opened up for him, had some so-so, routine matches to get to the final, and played pretty good in the finals but was he on his best form ever that match? That I don't believe.
Korda in my opinion doesn't belong on the list. Korda was basically considered a genius level talent by his peers, clear top of the food chain talent wise. McEnroe said he's maybe the cleanest, purest striker of the ball he's ever seen when on. He was an enigma type player, who when he should have been reaching his prime, had that part of his career taken away from him due to a groin injury he needed surgery for but was too afraid to get surgery for so he lived off pain killers instead and played at only about 60% of his capacity for a few years as he himself said, which is why his results "mysteriously" dipped during that time.
Korda was a French Open finalist in spite of having razor flat groundies. Korda was kind of like the Jana Novotna of the men's tour. They even had practically the same, ideosyncratic, Karate Kid crane kick, service motions. Same all-court game, fine hands at net, fine movement. But Korda had the more dangerous groundies. When he was on off the ground, he could totally decimate an opponent in no-time flat, before they even knew what hit them, it was like playing laser tag with a pentium chip assassin. At least with Gonzales, you know when you've been bludgeoned. With Korda, it was like being sliced up by a master Japanes sushi chef handy with blades. Before you know it, you've been skinned alive by a Schick Quatro razor blade.
Korda won the Australian Open in dominant fashion. He was clearly on a roll coming in, he beat Sampras at the US Open, took Sampras to five at Wimbledon that same year; he clearly was NOT the same hobbled Korda of the mid-90s, kind of like how Medvedev wasn't the same Medvedev from his top ten years. Things change for whatever reason, but clealry some guys have elite talent and others don't. Guys like Johnasson and Costa and Gaudio and Malivai Washington and Todd Martin to me all fall into the category of very, very good; but their talent was never so great that they caused a "buzz" among fellow tour players like Korda and Medvedev once did.
The Korda of the 98 Australian Open looked like a Korda who was on a mission, who was more mature and headier than in his earlier days when he made the top ten on talent alone. It just looked like someone who always had the talent, but learned to appreciate it and grow hungrier when he faced a difficult period in his life, and thus came out stronger for the wear, ready to now put it all together instead of squander.
Goran to me also does not belong on the list. Medvedev said in an interview upon retiring that there are several levels on the tour, that top 20 is very good but actually pretty much the same level as everyone else 20 to 100, just that they're more consistent in their level. He said that from 20 to 100, there's no difference, they're all the same level. He said that top 5, however, then that's totally different. He said top five is just on a different level from everyone else, that that's TRUE elite. Say what you will about Goran only having his serve and average groundies and volleys, but average but well-balanced groundies and volleys are more than enough when you've got such an overwhelming weapon as his serve. Players couldn't read it, and he could swing them out sooo wide as a lefty. Basically, if he was having a great serving day, it was basically unreturnable. In my opinion, more devastating than Sampras' serve even. Sampras was a more well-rounded server because of his great kick second serve (something Goran really didn't have), and the fact that he was much more consistent and reliable under pressure with it, but Bruguera said that when Goran was on with his serve, it was definitely the best in the world, not Sampras'. I honestly believe that to be true. Sampras, day in, day out, the better server, no question. If the match got tight, he was the less shaky server, the more clutch server. If you're just talking about when someone's in the zone once in a blue moon without the pressure? Goran was the king just as Michael Jackson was the king of "ee-heeh!" Goran's serve was unplayable if he was hitting his spots. Sampras, you could at least hope to get your racket on the ball...albeit just barely. Sampras wins the race, but Goran was the hare...of course, Sampras also just happend to be a really, really, REALLY fast tortoise though himself, not to take anything away from him.
Anyway, the bottom-line is that Goran was a legitimate top five player during his peak and no other tour player would argue that. If guys like Johansson, Gaudio, Martin, Berasategui, Washington, and Costa made top 5 for any decent stretch of time; I think you'd find the other players scratching their head...not that they don't think they're very good, but TOP FIVE good? That's a whole different level and story. As Medvedev said, there's really the top five and everyone else. Sometimes you can crack the top ten if you get on a roll for awhile, but I really think that to prove yourself to be a CLEAR top five level player at one point in your career shows that you are just a little more special than the rest.
Bottom-line, Korda and Goran, and yes Ferrero too (on clay), in the zone were virtually unbeatable as are virtually all top-five caliber players with the exception of Chang. Because of this, they are not fluke slam winners, but rather more cases of what took them so long?
Johansson, Costa, and Gaudio while very good, are just not quite on that level. Johansson and Gaudio are fluke slam winners. Costa was a warrior who overachieved Rocky style one year, still a fluke? Kind-of. It's the half-way point kind of like when the Rockets won the championship when Michael Jordon was busy going through a mid-life baseball crisis.