If you picked up a US-made Gibson and compared it to an Epiphone then you would probably notice a difference. The quality, setup and finish on a Gibson will almost always be superior. However, todays mass-produced guitars are far better than those made a few decades ago.

Whats the difference between Epiphone and Gibson?

Their tops are solid maple, while Epiphone uses a thinner sheet of maple and often combines veneer into their guitars. The hardware and the electronics that Gibson uses in the guitars are of higher quality as well. In the Gibson Les Paul, Gibson uses Burstbucker pickups; while Epiphone does use quality pickups.