You will see that SCOM 2012 SP1 have added predefined Resolution states.
I understand they have been introduced to SP1 for improved integration features like APM. I am not sure though if all the Resolution states listed were definitely intended for SP1 as the Technet docs only mention acknowledged..Feel free to add to this if you know any different.
I have not been able to delete the res states using either the GUI or the usual ‘Remove-SCOMAlertResolutionState’ Cmdlet
I suspect though even if you could, that removing them will break the future features so makes sense to leave as is. Of course if you are using the same ID’s as the Pre-Defined Res states then depending on how much customisation you have done on any connectors or views for example can vary significantly from one installation to another so the work effort is difficult to gauge.
I am of the opinion that resolution states should never be hardcoded as Res states have been used in so many different ways both when developing custom code, scripts, integration mechanisms as well as general views. This decision should be for the end client not driven by Microsoft.
One of my bug bears is when Views are hard-coded to only display New Alert  rather than display all alerts of any res state other than Closed . Whilst easy to resolve by creating a new Custom view it still is bad MP authoring.
one view that springs to mind which I really like apart from also suffers from this issue is the Alert View in the ‘Management Group Health’ Dashboard is fixed to only display Res . Very shoddy indeed.