I'm not sure I have an objective view in this, but I drove me to look at my own list of favored RPGs and what their designers did.
Jonathan Tweet's RPGs go Ars Magica (1987), Over the Edge (1992), Everway (1995), Dungeons & Dragons 3rd edition (2000). Of these, my favorite is Ars Magica, though I realize that opinions differ. It is at least still selling nearly two decades after its release. I think all of his designs are strong, though Everway was something of a flop.
Robin D. Law's RPGs go Nexus: The Infinite City (1990), Pandemonium! : Adventures in Tabloid World (1993), Feng Shui (1996), Hero Wars (2000), Pantheon and Other Games (2000), The Dying Earth (2001), Rune (2001). Like Tweet, I think he's clearly improved his craft, but I'd probably pick Feng Shui as my favorite.
Greg Costikyan's RPGs go Commando (1979), Paranoia (1984), Toon (1984), The Price of Freedom (1986), Star Wars (1987), Teenagers from Outer Space 3rd edition (1997). I'd have to put Paranoia as my favorite.
Mike Pondsmith's RPGs go Mekton (1985), Teenagers from Outer Space (1987), Cyberpunk (1988), Dream Park (1992), Cybergeneration (1993), Castle Falkenstein (1994), Champions: The New Millenium (1997), Dragonball Z (1998). My favorite of the lot is TFOS. The track is mixed with some of what I feel are real duds like Dream Park and C:TNM.
Sandy Petersen's RPGs go Call of Cthulhu (1981), Ringworld (1983), Elfquest (1984), Ghostbusters (1986), Hawkmoon (1986). Of these, my favorite is his first RPG Call of Cthulhu. While Ghostbusters was inspired, the others are pretty mediocre.
Steve Peterson's RPGs go Champions (1981), Espionage (1983), Justice Inc (1984), Danger International (1985), Fantasy Hero (1985), Hero System 4th (1989), Champions: The New Millenium (1997). Here, Champions improved in a number of things with editions and I respect Danger International which had a number of great innovations. But I hated the later Fuzion system. I'd probably put Hero System 4th as my favorite, though.
Ron Edwards's RPGs go Sorcerer (1998), Elfs (2001), Trollbabe (2002), Mongrel (2003), Black Fire (2003), Zero at the Bone (2004). Of these, I'm most interested by Sorcerer though I've only read the others.
My basic conclusion is that as far as my personal tastes, I think I am more swayed by inspiration than developed craft. Now, this is a little funny, because I am extremely concerned with good editing, polish, and attention to detail in RPGs. I do think that games do on average improve with later editions (though there are many exceptions) -- to the point that I am often hesitant to buy first edition RPGs. However, when I look at the track record, I have to admit I don't get a sense of linear improvement.
Now, some of my fellow Forgites might feel that the situation has changed in recent years, with designers learning from a new school. I'm skeptical. As far as I see from discussion and the profiling, hit games among the Forge crowd seem to favor the newcomer as much as the veteran. Hit games by my estimation would include Hero Wars, Sorcerer, The Pool, The Riddle of Steel, The Burning Wheel, My Life With Master, Primetime Adventures, and Dogs in the Vineyard.
On the other hand, I think I like it that way. RPGs are not a well-trodden field like the novel or the feature film, where classes can be given of accepted wisdom. It's still hit-and-miss, inspiration, and luck to a fair degree. I'd like to see more newcomers, new ideas, and so forth. There has at times been a danger of the Forge ceasing to be a place of innovation and instead seeing a lot of look-alike designs of a particular sort.
(NOTE: This was edited to add in Robin D. Laws, who should certainly be mentioned among top RPG designers.)