Over here there's no choice in the limit of cover - EU mandates that every car insurance has to cover 5 million Euro in personal damages and 3 million in property damage. The only "optional" thing is whether you want to get comprehensive insurance which covers your own car for the damage caused by yourself - but 3rd party liability is always set to that 5 and 3 million by law.

I guess you could buy some specialist insurance which would cover more but unless you are planning on crashing into multiple Bugatti Veyrons, it's pretty much impossible to hit that limit.