Do you have examples of good F2P games? I'd like to take a look.

To me, a bad pattern -- usually done by F2P games, but I don't think it's mandatory for them to use it -- is both the mindless grind ("am I having fun with this, or just clicking stuff?") and the pay-to-skip aspect. To me the latter is the worst, an admission by the game developers that their game is boring and the only way to get to the "good parts" is to spend money to fast-forward them. Usually there aren't even any good parts, it's all skippable.