Maybe the people most of all. But mountains, beaches, historic colonial cities, architecture, cathedrals, ancient ruins, pyramids, markets, food, weather and the list goes on and on. Do some research - lots of it. Read 1491 about the Americas before Columbus. Ask questions here. Everyone has a different idea. Some just hang out on beaches while others travel all over. When you ask what is the attraction we should ask what you might like - you may find it and more in Mexico. There are way too many attraction to even begin to list them all. You have to find your own.
Yes, there is crime, but there is crime everywhere in the US too. During the past 40 plus years we have been to Mexico many times and traveled in almost every state. We have never experienced crime or witnessed crime or met a corrupt cop. We may be the exception but we personally cannot attest to any of the bad things heard about Mexico.