Although we all do it, comparing yourself to guys on magazines is a bad idea. Here are just a few of the many reasons you'll probably never look like those guys:
1. The pictures are usually taken by professionals in ideal conditions. With the proper overhead lighting & shadows, even I can pull of a bit of a six pack, and that ain't saying much...
2. Along with lighting, oil/water can further enhance muscle appearance. That's why bodybuilders are always shiny with the stuff.
3. Pictures on magazines are almost always digitally edited. Bicep size is increased, waist size is reduced, lighting is edited, imperfections are airbrushed, etc. You can find MANY examples of this online.
4. The "pump": many of these guys workout right before the photo shoot (or the body building competition) so their muscles fill with blood and have a larger appearance. You can look way more jacked right after a workout than, for example, right after dinner.
5. Extreme diets: most body builders will do extreme diets right before competition that include all sorts of laxatives, drinking no water, eating next to nothing, and possibly many other drugs. It's the "lean" look you get in the morning times 1000. I suspect guys on magazine covers do this as well.
6. Drugs/chemicals can really enhance muscular appearance and I don't just mean steroids. There are many perfectly legal substances that increase blood flow, make veins come out, tighten the skin, etc.
7. Let's face it: these guys are on magazine covers for a reason. Because of all the above, they won't look as ripped in day to day life as they do on a cover, but they will still look pretty goddamn ripped.