It really depends on what your purposes are. Is it seeing all the content, or completing the game perfectly (including New Game+, if applicable)? Is that seeing every line of text that has been programmed? Good luck then with something like Little Busters. If you have three life-times to waste. Or even something like LittleWitch Romanesque. No one really knows how to unlock every one of those 1500+ events (some are rather straightforward, some are extremely obscure).
Seeing all the content, Super Powered will take some time.
Strategy games can be even worse, especially if they have multiple routes that are entered into early in the game.
Games like Sengoku Rance or Kamidori Alchemy Meister spring to mind. You only need to play 3 playthroughs for Kamidori to get all the content (provided you do the bonus stuff as well - and routes get decided early in the game, so it is not like you can do a quick reload, change your route, and be done in 10 minutes). However, if you are into pointless grinding, good luck since a lot of items are unique for a particular playthrough, and to even make all the items in-game you will need a few more playthroughs.
In Sengoku Rance, you will have seen all the content after 5 playthroughs if you play well enough (4 if you discount the Kill the Monkey route, and play well enough). But if you don't increase the difficulty, subsequent playthroughs can be a real breeze. At least you don't have to play through the game just to get more items.
But I am sure there are games out there where you will have to play through many more times to get to all the content.
