Best One Off Game Purchase

[Macman45]

Would like suggestions for a one off purchase that will really show off the graphics and power of my new iMac.

I like action games with a sic- fi theme like Dead Space ( already have it on my iPad2) Doom etc.

Not really keen on the COD series, and I've played most of them on A fast Windows PC anyway.

Ideas?,

 

[Macman45]

Sorry

I should have posted this in the Games section....Could a kindly Mod move it for me to avoid double post's?

Thanks