I mean we can squabble about what the definition of "most popular game of all time is", but if you're going with "the game that has sold the most units ever", it literally is: https://en.m.wikipedia.org/wiki/List_of_best-selling_video_g...

(TFA links to that page toward the end.)

This list by definition excludes free and free-to-play games, which is why Candy Crush isn't even on the list.

As for others talking about games like Pac Man: yeah, they were probably the most popular games at the time but the number of total players probably pales because the audience has grown considerably over time. I guess there's a strong case for Windows Solitaire though that seems to have somewhat of an age limit as I'd expect there to be a drastic cut-off for younger generations, especially since macOS became mainstream.

Which is?

Which is mistaking the most sales for the most popularity. There is a universe of games that have huge number of users, but doesn't sell copies.

Tetris and Windows Solitaire had a multi-decade head start though.

Snap, with real cards is up there.

What about Pacman?