At the end of the day, a compilation title is just one title no matter how many games it has, so adding the amount of games it has to a collection's item total is mere fluff. If by any chance having them counted is important, then adding that title to your collection based on the amount of games the compilation has could be an option. Like for example, Taito Legends 2 has somewhere around 30+ games, so add Taito Legends 2 30+ times to your collection. Quite unnecessary if you ask me, but hey, we all rock our boats however we want.
Perhaps entries for compilation titles could have a list of the games included in them for the sake of keeping those entries as informative as possible to any user that sees them. Note that this is actually something that I've pondered about a few times before, so might as well bring it up while it's fresh.