There are so many data sites out there, and unfortunately they have some widely varying numbers. One recent "study" came up with figures stating Las Vegas was lacking in parks per capita. It counted the population of the entire MSA, but only the parks located within the City of Las Vegas. The information out there can sometimes be confusing, especially without the details.
The Las Vegas - Paradise MSA is about the size of New Jersey. There are 4 entities in the actual Las Vegas valley, that covers an area of about 600 square miles. The City of Las Vegas, North Las Vegas, Henderson, and unincorporated Clark County. Boulder City is right next door in the Eldorado Valley. Even the Las Vegas Strip isn't in the City of Las Vegas, and you'd be surprised how many don't know that it's in the unincorporated towns of Winchester, Paradise, and Enterprise, NV. I have a map that shows where each area is located with the white representing the various unincorporated parts of the county.
Small Map 113KB
Large Map 1.28MB
It appears that some sites use a mix and match of information, and sometimes their own "formulas". City-Data reports the actual FBI Uniform Crime Report numbers for each jurisdiction. The FBI also urges caution when making crime comparisons, as there are a lot of variables that can effect crime numbers for an area. Las Vegas for example, has nearly 40 million visitors, a large number that aren't counted in the local population, and something that other cities probably won't have. So these are only a straight up comparison. Also note that Las Vegas will be reported as Las Vegas Metro that includes both the City of Las Vegas and unincorporated Clark Co., North Las Vegas, Henderson, and Boulder City report separately.
Another source that includes cost of living and other information.
Hope that helps, and Welcome to Fabulous Las Vegas!