I have always been baffled at the decision to give Dean Ambrose and Seth Rollins generic music given their potential to be top stars. Dean Ambroes' theme is a little more unique than Rollins' but I feel it doesn't fit his loose cannon gimmick as well as it should.
I tend to agree with this. If you think about it, most of the more recognizable entrance songs of the past have all been generic; we've just become accustomed to them. For example, Steve Austin had the glass shattering with pretty generic music following. The Rock had his catch phrase then generic music following as well. Same with the Undrtaker's gong, Mick Foley's screeching tires, even Brock Lesnar has pretty generic music. Point being, I think it takes time for that song to become exclusive to said superstar.
Rollins and Ambrose will continue to thrive whether their songs are changed or not.