If you find a closed question which you think should be reopened, vote to reopen it.
I hesitate to make any sweeping statements about a whole class of questions; doubtless some GR-closed questions will be worth reopening and some won't.
It's likely that most of them should be reopened according to today's standards - or possibly reopened and then closed for a different reason - but they should still be considered on a case-by-case basis. There's no such thing as a mass close-vote or mass reopen-vote; by the way the system is designed, questions have to be closed or reopened individually, and this is a good thing.
Without having looked at all questions closed as "general reference", I can't possibly say whether they should all be reopened. But if you think they should, feel free to cast reopen votes on all of them (preferably not all at once though - let's not flood the Reopen Votes review queue too badly) and wait to see how the rest of the community votes on them.