In realspace, small group roleplaying games, people rarely talk about who is or is not a good roleplayer. It's not really a relevant factor. People aren't usually competitive about it, or if they are, it's between "us and them" -- all of our group against other groups. But in larger groups like at cons, and in big multiplayer roleplaying games like MUDs, roleplaying suddenly becomes something where people evaluate who is a "good" roleplayer. So far as I can tell, there's virtually no correlation between who gets a lot of recognition, and who actually is doing anything interesting or challenging. What attracts notice is not usually good roleplaying but merely the appearance of good roleplaying, which is almost entirely mutually exclusive with the actual thing.
First and foremost, good roleplaying is about making an interesting and realistic character, who fits into the story, and helps make it better. A good character is like a person in that you can't sum him up in a couple of sentences. Who he is derives from his past, and isn't all immediately visible, but as you peel back the layers and expose apparent contradictions you eventually also find how they're not contradictions at all, at least not the kind that a person can't realistically have within them.
In a multiplayer game, odds are that most people who encounter a character like that will never realize what's really going on, as it should be. However, when they see someone who is a very simple, very loud, very overt, very over-the-top personality, and one which is not simply "I want to win this game" but something -- anything! -- more than that, they realize, ah hah, I see roleplaying. That, and that alone, is what tends to earn merit. Of course, it's childishly easy to make a character like that, but since most people don't, it still seems unusual enough to stand out.
But it's not enough to be loud and obnoxious. There's one other element you need. See, most people play characters very like themselves, with similar attitudes, likes, and motivations. This is even more prevalent in long-term games (since you're going to have to live with that character for a while) than shorter-term games. Thus, most people assume that other people are very like their characters, and therefore, tend to dismiss roleplaying they're seeing as being merely an expression of that. However, if your character's personality or behavior is something the player clearly cannot really be, if only because a person like that would not be playing the game, then suddenly the same behavior is judged not a revealing appraisal of the player, but instead, a sure sign of roleplaying chops.
Ultimately the people who get the credit are people who have taken only one step away from "just play myself and treat it as a game" but once you get a second step into roleplaying, or more, you drop off everyone's radar. The more realistic and deep your roleplaying, the fewer people are likely to recognize it. It's a lot more so than how subtle but good acting isn't as easy to spot as brash and obvious acting: in those cases, critics and movie fans are actually looking for it. Everyone knows everyone's acting; no one mistakes actors for people playing themselves. Recognizing a better but subtler performance takes a little attention, but no more than that.
Sometimes I hope I can see some of the people I encounter in Lusternia twenty years from now, so I can watch them starting to realize the things I was saying to them all along. But maybe that's just a mix of schadenfreude and patronizing contempt, neither of which look very good on me. It's just that they're so young!