The Fine Line is excellent. But I'm a fan of these water shows (love "O" in Las Vegas) so I might be biased.
1887 - Good ice show. Makes use of the projection effects you see at NBA and NHL games nowadays
Columbus the Musical - Probably the best "secondary" musical/revue I've seen on a cruise ship. It's a "jukebox" musical, and unlike Wishes or Believe there's actually a decent plot and proper transitions between the set pieces.
Comedians - I had Jim David on my cruise. Kind of weird to have a name that I've heard of before, but I like his stuff.
Grease - Not a fan of Grease, so didn't see it.
Featured performer - Had a Motown singer. He was good, but not my thing.
There was also a guy with a gimmicked piano going all around the ship singing - ironically - Disney show tunes.
If you email
Royal Caribbean customer service about 1 month ahead of your cruise they should be able to tell you who the comedian and feature performer are, as well as some of the acts in the bars and lounges.