A just published study (actually still in preprint) suggests that Earth like planets may be quite uncommon. I’m a little skeptical about the reasoning (based on the discussion in the link: I haven’t read the paper). It’s quite possible that the reason we haven’t found system’s like Sol’s is just that we don’t yet have the capability. The existence of systems which evolved in an entirely different way doesn’t really bear on the number of solar systems like our own except very indirectly.