If you play lightweight indie games, games that use OpenGL or older DirectX games you should be fine but check for support.
If you play games that use DirectX 9 check and make sure they are supported.
If you play games that use DirectX 10/11 and like to get new releases don't even bother trying.
If you just want to play your games and not be concerned about OS issues or support for that new game that is coming out then use Windows.
You might want to try installing Linux inside Windows so they share the same partition using something like Wubi
You should also consider using a VM running Linux in full screen or with something like VMWare Unity so you can get you Linux applications and not have to reboot the computer constantly.
You can use a 3rd party application in Windows for reading ext4 filesystems here is a write up on some of them... but you would have better luck reading/writing to NTFS from Linux using ntfs-3g so I would recommend you give the majority of the space to the Windows partition and give your Linux partition like 40GB or so depending on what you are doing on it.
If you have a 1/2/3TB HDD then you could partition off like 500GB for Windows/Games and you should be perfectly fine unless you are installing a ton of games.
You can create an NTFS partition for Windows an EXT4 for Linux and a FAT32 mutual partition for sharing files as both systems support it.