If I understand correctly¹ what the English sentence means, that might be:

Tu [en] as de drôles de façons de t’amuser !

Or the colloquial:

T’es un peu chelou, toi !

¹_{I guess I did, Flying_whale had the very same sentence in mind too…}

Aside from the already mentioned “Tu as de drôles de façons de t’amuser !“, if you’re going for something sarcastic:

Ah bon… C’est original, comme façon de s’amuser.

Good answers already :

• This one, lightly facetious
  _{Tu [en] as de drôles de façons de t’amuser !}
• …and that one, a little more sarcastic
  _{Ah bon… C’est original, comme façon de s’amuser.}

To add more examples on the sarcastic side, I suggest :

• Ça amuse les enfants ! → common in the area of Quebec where I grew up, back in the nineties. It has remained to this day, but it’s somewhat less used now.
• On s’amuse comme on peut… → implies to a certain point that the silliness of the game is a consequence of a poor imagination.

The following suggestion is slightly off for it doesn’t directly call into question the level of strangeness of someone’s idea of fun, but rather how low they’ve set their “fun-bar” (i.e., how little it takes to amuse them), but it can, at least, be used to poke some good-natured fun at the activity and those who consider it to be fun:

Ça t’amuse vraiment ? Hé bien/Alors, il t’en faut {vraiment} peu {pour
t’amuser/pour être heureux/euse}
!

(follow the above link to a WordRefernce.com thread discussing “il t’en faut peu”)