They are quite superior athletically. We see that every day if we are sports fans.Le Bron James/Michael Jordan? What white can touch them? Basketball TOTALLY. Football pretty much.
Where else might jealousy/envy exist? Well I'm not one to spread rumors. Suffice it to say there are other areas where they are said to be superior. I leave it to you to figure out what they may be.
Jealousy? Very likely.
We have to be careful though. That stereotype of blacks being inherently more athletically gifted than whites is very common and very widespread but has little or no physiological foundation. If that ability was due to ethnicity, the most athletic would probably be of Nepalese or Peruvian, not African, ancestry.
The apparent greater successes by ethnicity are results of society, culture and opportunity, instead.
It's not the only flawed stereotype that gives ethnicity or nationality supposed advantages in particular fields. Related myths are that being a Central European (German or Italian) grants a propensity to creating great music; that an Indian (Asian, not American, "Indian") axiomatically has the brains to be a professional mathematician or computer-programmer; or much more destructively and of greater antiquity, that being Jewish attracts money.