Given the way things have been revived since the turn of the century, I'm surprised at how few of the 90s musicals have been revived. City of Angels ('89, but come on) could have been revisited. The Secret Garden is definitely due for a revival. Grand Hotel, Will Rogers Follies,
Also, literally any of the shows that kept Broadway afloat during the very worst of the AIDS crisis. They may not deserve to be recognized for their artistic merit, but their contribution to the genre is invaluable and I'd love to see them again in their proper context. (Of course, some of them were really good and are still running today.)