Estimating the priority of a bug or a feature is often not as straightforward as it should be: the importance of an issue is relative to who is considering it and can be exaggerated or downplayed to suit various needs. When faced with the prospect of some bugs not being fixed, stakeholders decide they are all 'highest priority' making your role all but impossible: if there is no agreement on the problem there can be no agreement on the solution.
If you aren't familiar with it, you should look into using the MoSCoW rating system where issues are classified as either:
Must fix: Must be fixed before launch, no matter what. Anything in this category is so important that it will justify people working overtime or delaying the submission.
Should fix: Should be fixed if we have time. Anything in this category is not so important and should not impact working practices or project timelines.
Could fix: Could be fixed if we had time, but we don't so it will be moved to the next version. If there is no next version, this issue will not be fixed.
Won't fix: This issue will not be fixed and can be archived.
Because this rating uses natural language, when an issue is raised it is possible to verbalise (or get the stakeholder to verbalise) which category the issue falls in simply by talking about it and seeing which adjectives are used without being prompted.
Alternatively, you can ask the stakeholders to define how much the fix is worth to them (Paying for overtime? Delaying the project?) and the answer will place the issue straight into one of these categories.
No one wants to ship a product with bugs, but if there isn't time to fix them all then hard choices will need to be made. The MoSCoW rating helps you manage those choices.