They are about 10x the next best (Techstars) based on valuation of the companies they've funded (~$80B vs ~$8B). Valuation isn't a perfect metric, but it's a reasonable proxy for performance.
That said, the total number of companies funded isn't that different. We're at ~1400 and according to the below, TS is at 1000: https://www.techstars.com/content/accelerators/growing-world....