it depends on whether you define 'legend' as the overall persona of a player or their overall achievements. both can be very different, for instance kournikova is a legend of womens tennis if we talk about transcending the sport, but obviously not one on court.
i always feel mcenroe was hugely helped to reach 'legend' status by his persona where his results lacked.
You need both. A huge personality is important but you need the results to go with that. If you get to 6 or 7 majors and have a memorable personalty to go with those results people will idolise you forever. Kournikova is only remembered for looks, sex sells