My grandfather bought me an Erector set, and it was one of the best toys I ever had - but it definitely required a larger investment of time and effort than Lego did. Before you even consider that you need to plan out or follow instructions to build a machine, it just plain takes longer to connect the various pieces, with the fiddly little nuts-and-bolts that you steadily lose over the years anyway.

I have a kid, now, and I definitely look forward to getting to play... or watch someone play... with Erector sets and Lego and all those toys.

edit: Thinking about it some more, Lego is Minecraft, and Erector/Meccano is Kerbal Space Program.