Well, kerneloops doesn't include much data from real crashes, since it's usually too late for automatic submit of crash log once the machine completely stops responding. Well, you can grab the panic message via serial console and post it to bugzilla or mailing list, but nobody does that for nvidia drivers for obvious reason.
Secondly, most kerneloops data is collected from bleeding edge and development releases. More reports from non-nvidia hardware generally mean more development is happening there.
When it comes to stable Linux-based OS-es, let's consider RHEL 5 (I haven't used other comparable OS-es, but I believe most widely used enterprise-class distribution is a pretty good example). ATi and Intel works mostly flawlessly there compared to NVidia, which for example can not resume from suspend, or freezes for minutes (on T61, again fairly common platform). And no, no kerneloops messages were sent for it.