Before this turns into a bashing exercise in one of the famous flightinfo unprofessional free for alls, there's no need for name calling. Flyf15 asked a simple question, and the answer is just as simple; flying is as safe as you want to make it.
Take that 172 flight, for example. You can make it in many ways, some of which are not at all safe, others are, but only so far as you allow the to be. You fly from A to B. You do it at night, and when you have a failure of your single vacum pump, single generator, or other problems with your minimal equipment, you have instrument losses, system losses, failures that have no backup, and if you have an engine failure (never a matter of if, but when), you can't even plan a proper forced landing because you can't see anything.
Modify that a little. You're over a metro area with good highways beneath you, it's late, light traffic, you know the roads, you know the powerlines, you know the surface, and you are confident that you can make a forced landing if you need to. There's more light in your cockpit than you really need due to all the light from below. You don't need any instruments, it's as good as day below. You make the flight at night no differently than you would in the daylight, execute a dozen night landings at your favorite runway, and enjoy a ride home in smoother air than the daytime. You find it relaxing, spiritual.
Two sides of the same coin, all in how you elect to make the flight. You make a cross country, take three quarter tanks, plan on using a full half tank, so you'll arrive with quarter tanks. Well enough, you have your reserve, but lo and behold, you didn't catch the wad of leaves put in the tank vent by the leaf cutter bee, and you got an uneven fuel flow. By the time you're nearly to your destination, you have plenty of fuel because the engine runs dry...you're sucking air feeding from the tanks when it's not really feeding, and one tank has run dry. Change that scenario to no mechanical issues, but the unwise decision to run a tank dry before switching...and now you can't get the engine started. There are ways to make it safe, and ways to not make it safe.
In the airline world, you have small windscreens and large areas to cover. Youré in and our of metro areas with high traffic, then up into the "safety" of the airways. You seldom look out the window, seriously scanning for traffic, at cruise altitude. But you also know that when you first got TCAS, you were shocked at the amount of traffic that's out there that you don't see. Now you're jumping into a light airplane equipped with what you bring; your two Mark I Eyeballs, and a neck to swivel them about. As safe?
That's up to you.
Certainly the radio and ATC won't find that traffic for you. That's up to you. Certainly TCAS won't help you, because you won't have it. Nor should you be heads down any more than necessary; look for that traffic as though your life depends upon it, because of course, it does.
Your airliner has aircraft data by which you fly. You have much of it done for you, but you also do some yourself. No reason why you can't calculate the same TOLD data along with your weight and balance. Some call it overkill in a light airplane, but it's not.
Think about the notable midair collisions over the past few years...how many of them have been in controlled airspace, while talking to ATC and participating in the system? The vast majority of them. Did this make them safer? Of course not.
In general aviation, the type of "accidents" continue to be boringly familiar; they stay the same. Infrequently is the airplane or gyroplane or helicopter or balloon or sailplane at fault. Invariably, it's the pilot that runs out of fuel, continues VMC flight into IMC, strikes terrain while flying low, fails to properly preflight, loses control in convective weather or in ice where he or she shouldn't be, or the ubiquitous and freakishly popular stall-spin during the turn to final (or turn back to the runway after an engine failure, take your pick). The list goes on. The common thread is that in each preventable occurance, the deciding factor isn't the safety of general aviation, but the pilot. How safe is it? That's up to you.