The difference between England and the rest of the Test Nations is the strength in depth we have. Look at some of the players we have that aren't playing in this test - Trott, Tremlett, Finn, Davies and Panesar (still a very good spinner). Add to them some of the younger players coming through (Woakes, Taylor, Kieswetter, Dernbach etc). As has been shown, take Trott out of this team and Bell can step up to Number 3 and post back to back centuries. Take someone like Kallis, Zaheer, Watson et al out of their respective nations and they have nobody to step up to the plate.
On the point somebody raised about Bell not getting the laudits he deserves in England I take it you don't read much cricket press or listen to the commentators, all of whom say he is by far the best technically gifted player around today.