Or just take a look at Jack & Daxter trilogy (PS2). First part was a nice (ok ok, 3D) jump'n'run. But then, the second and third part. Suddenly it was a GTA SciFi clone.. +o(+o(+o( with weapons, vehicles, open city... nonsense².
Imo jump'n'runs should stay jump'n'runs. Sonic, Mario and other...