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Sure, there are some great ones, but there are quite some reasons why I wouldn't play one.
I mean sure, you can download them, try them and play them for free. But if they are great, you're probably going to pay €€€ anyway. And if they are bad, then you wouldn't want to play it anyway. In addition to that, you often get less depth or less content. Not always, but often.
As said, I don't think all F2P games are bad or that people who play them are doing the wrong thing. But I personally tried quite some F2P games and up to now found none I'd have more fun, without paying anything, than with a P2P one.
The only games I play where I spend money on in irregular intervals and which you could compare to a F2P game with an item shop would be MTGO and BF. But for both of them is simply no similiar thing available online that you could else play.