Which is taller, Burj Khalifa or Ayers Rock/Uluru?

Burj Khalifa is taller than Uluru.

Burj Khalifa stands 828 metres tall.
https://www.burjkhalifa.ae/en/the-tower/facts-figures
Uluru is 348 metres above the surrounding land, and so is much shorter.
https://parksaustralia.gov.au/uluru/people-place/amazing-facts.html

It is worth noting that the top of Uluru is over 860 metre above sea level, so it has a higher elevation than Burj Khalifa. Height above sea level is, however, not the criterion for tallness, or we would have to consider a storage hut near the top of Mt Everest as the world's tallest building.