The ones I am thinking of are in the environmental and planetary sciences subfield. Specifically, ETH is well known to me for their strengths in atmospheric modelling, physics of fluids etc. I am sure there are other strengths too, and I've met grad students in physics across many fields, but I just don't remember specific people other than the ones in related research.
As for your second question, this is not really a well-defined question. There's no ranking of people like that and I'm not sure how useful it would be if there was. If you are asking whether ETH is as well known as a name as Imperial/Oxford/Cambridge, then I would say yes.