Like I said, climbers tend to be relatively type-A people (notice the hyphen) who focus on technical details and like ticking climbs and mountains off of checklists. In addition to doing difficult climbs, mountain lists and completing them are one way we enjoy our sport and measure ourselves against each other. And we have a lot of them.
What makes a good list depends on a lot of things. Brutal mountain difficulty and high-level adventurousness factor in, but they're not the most important aspects of a good or popular list. Most lists are regional and based on a certain height. The US' biggest and best-known list is its 50-odd 14,000-foot peaks, or Fourteeners. 14,000' is important because, outside of Alaska, the US has no mountains taller than 15,000', making 14,000' plus change the highest mountains the country has to offer. A lot of regions, like New England have a peak list based on a locally high elevation that contains a reasonable amount of mountains, like its four-peak 5,000-footer list or its 100-and-something-mountain 4,000-footer list. A good list takes a while to complete, has some (at least locally) iconic and well-known peaks that get climbers interested in the list, but also has some poorly-known ones that will take you to new areas you probably would not have otherwise have gone to, whether the individual peaks are difficult or scenic or not. The Seven Summits even meets these criteria, because it contains peaks of mixed difficulty and diverse location, including some no one would ever know about if they weren't on the list (e.g. Antarctica's Mt. Vinson). "Highpointing" or reaching the highest point of a set of political units, like US States or European nations, is becoming a really popular offshoot of this idea because it strongly meets all of the above requirements. There are a lot of groups dedicated to various forms of this.
I chose Africa's Big Five mountains as the basis of this project because it meets all of those criteria well. Were I to do it again, I might have swapped out Mt. Meru, Kilimanjaro's very close neighbor, with a different mountain that's more geographically distinct from the others for those reasons, much in the same way that I only summitted Mt. Stanley of the Ruwenzoris instead of doing other peaks within the mountain chain. Rwanda's Mt. Karsimbi would make a good substitute. Doing all of the East African Community's five highpoints (so Kenya, Tanzania, Uganda, Rwanda, and Burundi) would also have made a great list, even though Burundi's highest "mountain" is a hill near its border with the DRC. No list is perfect, but the idea is to have an interesting and challenging adventure that brings you to areas you'd never see otherwise (western Uganda, for instance).
And with that, I've been writing all day and it's dinner time. Enjoy!