While I can't (yet) find a central list of success rates, numerous operators boast theirs on their websites.
However, as some sites point out:
Even though outfitters and tour operators flaunt high success rates,
official statistics indicate that a very high percentage of trekkers
turn back before summiting Uhuru Peak. It is quite "an
accomplishment" to summit the mountain. Generally, the longer one
allocates the trek, the higher the success rate of reaching the top.
Most seem to be fairly similar though in their claims:
Wiki shows that there are five or six common routes, and depending on the route, the success rate changes - Machame is the one with the highest success rate, followed by Shira or Lemosho.
A great description of the routes and their chance of success is available here.
The best I can find for stats is from Team Kilimanjaro, who have a comprehensive discussion of the misleading statistics out there, and why you should choose the route you choose, and what counts as a 'success' on a climb.