Conina on 21 April 2018
I just looked up the game which I have the most versions of.
And the winner is... Defender of the Crown. My "Extended Collector's Edition" (limited to 500 units) contains the following versions
- Amiga CDTV version (CD-ROM)
- Amiga CD32 version (CD-ROM)
- legal emulation of the classic Amiga version
- legal emulation of the extended Amiga version
- legal emulation of the Amiga CDTV version
- legal emulation of the Amiga CD32 version
- legal emulation of the CD-i version
- legal emulation of the C64 version
- legal emulation of the Apple II GS version
- legal emulation of the Amstrad CPC version
- legal emulation of the ZX Spectrum version
- legal emulation of the DOS version
- legal emulation of the Mac version
- legal emulation of the Atari ST version
- legal emulation of the NES version
I also have the Android version based on the Amiga version.
Okay, that was a bit of cheating cause I bought all of the above (except the Android app) as one product. 
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Oh, I bought 8 versions of the point&click adventure "Machinarium" in that order:
- Steam version in 2009
- then I got it in a Humble bundle
- PS3 version (flash sale)
- GOG version (Collector's Edition)
- iPad version
- Vita version
- Windows Store
- Android
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Day of the Tentacle:
- retail CD-ROM (English version)
- retail CD-ROM (German version)
- DotT Remastered (PS4 / Vita Cross-buy)
- DotT Remastered (Steam)
- DotT Remastered (iOS)
- DotT Remastered (GOG)
- DotT Remastered (Twitch)
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Grim Fandango:
- retail CD-ROM (English version)
- retail CD-ROM (German version)
- GF Remastered (PS4 / Vita Cross-buy)
- GF Remastered (Steam)
- GF Remastered (GOG)
- GF Remastered (iOS)
- GF Remastered (Android)
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Limbo:
- Steam version
- GOG version
- PS3/PS4/Vita cross-buy
- Xbox One version
