Sudoku is kind of third grade math homework mixed with elements of a crossword puzzle. It's not exciting, but like most pasttimes, it passes time. Not really my thing, but I see people doing it on the subway, probably because it's easy to get into or put down, and requires very little overhead.
Sounds like you've got about enough experience with fighting games and RTS that I can say you have no idea what the hell you're talking about. I could just as easily trivialize 4X games as "make a bunch of colonies, research the whole tech tree, and win". It would probably be about as fitting and apt as your descriptions of either of these two genres.
Try mashing one button against a player of my skill in Tekken. It'll be funny
and educational.