there aren't 10 players better than bird, shep. stop trolling
even if your crusade to move duncan ahead of larry bears fruit, bird is still top 10.
i think the biggest factor in making the top 10 is having left an impression of dominance, of being the best over a period of time. it doesn't have to have been real dominance, just to seem that way to people at the time and leave the sense that they were unquestionably the greatest for a time. i honestly think that's why mj gets so much hype for the top spot. he was seen as being not just the best, but indisputably the best player in basketball in 6 or 7 different years. even when he didn't win the mvp, by the end of the finals all the talking heads were raving about him again.
kareem had an even longer run (which led to more mvps), but interest was light in the 70s, and he didn't do much of his winning until the 80s when the best player poll kind of swung between him, doc, and moses and then around 84 swung firmly to bird. then magic was seen as the best from about 87 or 88-90 with jordan and bird drawing some of his heat, but not enough to lower him.
in the middle of mj's run, he retired, and hakeem got the props for putting up great numbers, winning, and beating his best center competition head to head in the process. he's a marginal top 10 for a lot of people and i think that's for 2 reasons - 1st that he had a short run of dominance and 2nd that a lot of people want to count mj's absense against him, which i find stupid.
then you've got shaq who was very good from about 95-2005 but only really had people calling him an unstoppable machine for about 4 years from 2000-2004. nobody questions his place in the top ten though because he had no equals for at least three of those years. right now there is, i think, a sort of back and forth swing in perceptions over whether kobe's transcendant abilities or duncan's steady winning makes one or the other the top player of the last five years. duncan seems like a lock to stick in the top ten because when the post season ends he sticks in people's minds as the best so often, but kobe could climb up there with him before it's all said and done just based on spectacular performance.
going way back, people seem to sort of have a quad dominance perspective of the 60s / early 70s. wilt for his towering stats and larger than life game and russ for his desire and consistant winning. then on the perimeter west and oscar for their huge stats and just the level of separation they seemed to have from the other guards of the era. mikan's dominance i think is questioned because of segregation which was still a big part of the game during his playing days and because the game was in its nascent stages in general. right or wrong, just perception.
moving forward i think it's sort of a race between bron and kobe. will bron's game get better and kobe's drop off quickly enough for lebron to be seen as the solo best for a long, long time, or will kobe hold him off for a few years and extend his own chances of being remembered as the best player of 5 or so years? or will somebody else leapfrog both of them?
again, to me it's all about perception, dominance, and in some cases (i'm thinking mostly the older guys, mike, and duncan here, but it's really true of most of them) sustained excellence over a career.